Channel-forming equipment for trunk connections. Automatic telephone exchange Equipment TT 48 technical description
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Equipment P-327-12
Tactical and technical characteristics of the P-327-12.
The P-327 military equipment complex is intended for the formation of voice-frequency telegraphy (TT) channels and low-speed data transmission channels (TD) in networks and on direct communication lines of various control levels.
The P-327-12 equipment can work with the military equipment P-318M-6, P-319-6, as well as with the equipment of the national network TT-144, TT-48, TT-12, TT-17P.
Purpose.
The P-327-12 equipment provides twelve 100-baud TT channels in one voice frequency (VoF) channel or six TT channels in two VT channels.
In six-channel mode, it is possible to connect a telephone (TF) intercom of P-327-TPU equipment to each semi-set of P-327-12 equipment.
Normal operation of the P-327-12 equipment is ensured at ambient temperatures from -10 to +50 °C.
Using channels.
The CT equipment channels are designed for connecting TG devices operating with currents in two directions with separated transmission and reception circuits.
To connect TG devices operating in single-band transmissions with both separated and undivided transmission and reception circuits, adapter devices located in the P-327-PU6 and P-327-PU1 equipment are used.
Composition of the main equipment.
- Equipment P-327-12
- Operational documentation
- Linear shield.
Management and control system.
The equipment provides optical alarm signaling:
- loss of signals at the output of the transmission path,
- loss of supply voltage,
- malfunctions in generating equipment
- about a decrease in the reception level by more than 25 dB compared to the nominal
- loss of transmission level.
The equipment provides the ability to adjust the dominance in the TG channels by ±20%.
To check and configure TG channels, the equipment contains:
- 1:1 view CW sensor (dot sensor) with a nominal speed of 200 Baud
- indicator of dominance, ensuring the accuracy of elimination of dominance is not worse than 3%.
Operating modes and electrical parameters of the system.
The P-327 equipment is a multi-channel voice-frequency telegraphy equipment with frequency division and frequency modulation.
As already indicated, the P-327-12 equipment can operate on one or two PM channels.
The first mode is conventionally called the 1PM mode, and the second - 2PM.
In 1 PM mode, the equipment forms twelve TT channels in the PM channel at a speed of 100 Baud in the band 0.3 -3.4 KHz
In 2TC mode, the equipment is circuit-divided into two independent parts, each of which operates on a separate TC channel, forming six TT channels with a speed of 100 Baud in a band of 1.8-3.4 kHz, i.e. in a channel band of 7- 12. In the 0.3-1.6 kHz band, business telephone communications can be obtained using P-327-TPU equipment.
The P-327-12 equipment is connected to the PM channel only via a 4-wire circuit at channel points with relative levels of - 1.5 np (-13 dB) and + 0.5 np (4.3 dB).
The attenuation of SL-1 should be no more than 1.15 np (10 dB). This corresponds to the SL length for the cable:
- P-274M - 5 km,
- P-268 - 10 km,
- ATGM - 4 km.
Connecting lines to telegraph devices can be either 2-wire or single-wire (wire-to-ground). The length of connecting lines (SL-2) can be within the following cable limits:
- P-274M - 5 km,
- P-268 -1 0 km
Basic electrical characteristics of channels.
P-327-12 equipment channels telegraphing speed up to 100 Baud. It is possible to increase the speed up to 150 Baud by increasing the edge distortion of TG signals.
The transmission levels of each channel of the P-327-12 equipment at its linear terminals are equal to -32.5 dB (-3.75 np).
The nominal reception levels of the P-327-12 equipment are -15.5 dB (-1.73 np).
The average signal power of all TT channels of the P-327-12 equipment, reduced to points with zero relative level, is 135 μW.
The input and output resistances of the P-327 equipment on the side connected to the TC channel are equal to 6000 m. Permissible resistance deviation is no more than 210 Ohms.
The input resistance of the TG DC transmission circuits is 1000±1000m at an input voltage of 20±5V, and the receiving circuits do not exceed 5100m.
The TG supply voltage of the transmission circuit is ±20 V. The channel’s operability is maintained at a voltage value from 5 to 30 V. The nominal current value is 20 mA.
The supply voltage of the TG receiving circuits is ±20 V. The permissible voltage deviation is from ±9 to ±25 V.
The difference in voltages of positive and negative polarity does not exceed 7% of the average value of this voltage.
The ripple coefficient in TG receiving circuits does not exceed 3%.
Telegraph circuits allow the inclusion of an additional external power source with a voltage of 60 V.
The frequency band of each CT channel is f1-f2 = 160 Hz.
Filtering bandwidth - 80 Hz;
The average frequencies of the channels are selected according to the formula:
Fav = 240+240n Hz, where n is the channel number.
Frequency deviation f = ± 60 Hz.
The characteristic frequencies in the channels are equal:
- fнn = fср - f
- fвn = fср + f
Here fнn and fвn are the lower and upper characteristic frequencies of the nth channel.
In the P-327 complex, signals of positive polarity correspond to the lower, and signals of negative polarity correspond to the upper characteristic frequency. If there is no current in the telegraph transmission circuit, the upper characteristic frequency is transmitted.
The permissible deviation of characteristic frequencies from the nominal values at the linear outputs of all types of P-327 equipment is no more than ± 1 Hz.
Operating modes of TT channels.
The equipment forms telegraph channels in mode 1. To switch to modes 2 and 3, you must use P-327-PU-6 and P-327-PU-1.
Mode I - Mode of operation with currents in two directions with separated transmission and reception circuits. Designed for connecting terminal telegraph devices operating with bidirectional currents (CA) to the channel. Transmission and reception currents 20 +- 5 mA.
Mode II - operating mode with currents of one direction with separated transmission and reception circuits. Designed to connect two telegraph devices to the telegraph channel to the reception path and transmission path through adapter devices P-327-PU1, P-327-PU6.
Mode III - mode of operation with currents in one direction in unseparated transmission and reception circuits. Designed to connect one transmitting/receiving device to the TT channel through the P-327 - PU6(1) adapter device.
Power supply, mass.
The P-327-12 is powered from an alternating current network, with a frequency of 50 Hz with a voltage of 220V+10=15% (187-242) V on control systems and stationary objects or with a frequency of 400 Hz with a voltage of 115V+6V (109-121) V on aircraft, helicopters (VZPU), power consumption from the alternating current network is 100 VA.
Equipment weight: 55 kg.
Set weight: 78.5 kg.
Dimensions: 673 x 386 x 271.
Equipment design P-327-12.
The design of the P-327-12 is based on the principle of basic channel formation, which consists in the fact that to obtain multi-channel communication systems, one basic channel block is used. The number of basic channel blocks determines the number of channels in the equipment. All channel blocks are the same and interchangeable.
The placement of the general linear spectrum into the appropriate frequency band, depending on the operating mode, occurs at individual conversion frequencies. All P-327-12 components are mounted in separate blocks with engraving on the front panel.
- BLN - linear voltage block.
- S-3 - signaling unit third
- S-1 - signaling unit first
- I - measurement block
- CHZB - frequency block (for working with P-318M)
- CHZA - frequency block (for working with the same type of equipment)
- BH - 2 blocks of frequency dividers
- K - frequency switching unit
- SN - voltage stabilizer block.
- PIT - power supply unit.
- KP - 2 predominance compensation blocks.
- TG - 12 blocks of telegraph devices.
- K-100 - 12 channel blocks.
- L0 - 2 blocks of linear equipment.
PUPR
SMO
SFKU
Drawing. Block diagram of the CFB
OMV – designed to ensure parallel operation of two computers. Each computer contains:
Processor, to perform all arithmetic and logical operations;
RAM, for receiving, storing and issuing information;
A multiplexer channel that interacts between RAM and airwaves.
Selector channels through which information is exchanged between RAM and VSD.
The VK also includes: a printing machine, an alphanumeric printing device, and a punched card input/output device.
VSD – designed for storing large amounts of information, entering data required for processing and outputting the results of this processing. NMD and NML are used as VZU.
SMO - designed to implement message switching tasks on a VC, ensuring the required qualities, message processing performance and high reliability of equipment operation. It consists of a set of programs, which, depending on the functions performed, are divided:
OP - organizing programs;
TP – technical programs;
PUPR – programs for controlling the parallel operation of a computer;
TSP – test programs;
SP – service programs;
SFKU is designed to ensure control and compliance with the requirements of general and technical operation in the UKS. The structure of SFKU includes:
SD – dispatcher section,
SIT – telegram indexing section,
SOVT - control and reference service,
STC – technical control section.
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Algorithm for interaction with the end point, with the circuit switching network, MSS-MSS.
The interaction between the MSC and the MSC is carried out in simultaneous transmission mode. If the channel is in working condition, the MSC checks the message format, header and content. If an incorrect format is detected, as well as errors in the header and text, the MSC sends a request to the adjacent MSC-T and puts the channel into a communication recovery state. Upon receipt of confirmation that the adjacent channel has accepted the request, this MKS-T puts the communication channel back into working condition.
The adjacent SKS-T repeats the transmission of the distorted message. If confirmation of receipt of the request is not received by the given CKS-T within the control period, the channel is transferred to the dispatcher blocking state. In this mode, this CKS-T does not accept incoming messages. To put the channel back into working condition, special procedures must be provided, for example, operator intervention or automatic transmission of a request after a certain time.
The interaction between the CKS-SKK-OP is carried out as follows. CKS-T are connected by SCCs with separate (outgoing and incoming) bundles of 50-Baud channels. The maximum number of channels in a bundle is up to 50. In the SCC, the direction from the CCS is crossed as the direction from the register station. Telegrams from CKS-T (except for telegrams of urgency category P, processing categories K, B and circular transmission) are sent via dial-up connections, i.e. CKS-T dials the number sent to the SKK, the SKK makes a connection with the required OP.
When receiving a refusal, the CKS-T can make several attempts to dial a number for a connection at regular intervals over a certain period of time (depending on the control period for processing telegrams of this category). When a connection is established, automatic replies (AR) are exchanged. Moreover, the details of the telegram necessary when searching for it are added to the last AO.
The direction to the CKS-T is cross-linked in the SCC as an out-of-zone direction. To establish a connection with the CKS-T, the OP operator dials the same six-digit number, which must be indicated in the telegram preheader. They are given the opportunity to transmit a series of telegrams (no more than 5) in one connection to the CKS-T. Moreover, each telegram in the series is preceded by AO OP and TsKS-T and is also completed by these AOs. To JSC TsKS-T, transmitted after receiving the telegram, its details are added.
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Message formats
One of the performance indicators of the central communication system is the use of standard message formats. Message format is a formalized arrangement of its individual elements, allowing for its automatic processing. Message format when transferred from the OP to the MSC:
3Ц3Ц 002 AP 008 837
Telegram header
Telegram text НННН
In the first line of the telegram subheading the following is indicated: sign of the beginning of the telegram 3Ц3Ц; its serial number is 002, under which it is transferred from the OP to the CKS; urgency category A; processing category P; main index 008; low destination index 837; end of pretitle .
The second line contains the telegram header and the end of the header.
The third line contains the text of the telegram and the end of message indicator НННН.
The serial number changes cyclically from 001 to 999. Telegrams have 5 urgency categories:
A - air telegram,
C - urgent,
P - simple,
B – festive (congratulatory).
K – cryptogram (encrypted),
B – especially important (government),
P – transferable (money transfer),
C – circular (to all OPs at once).
The main index determines the zone, and the lower index 837 is the point (post office) for receiving a telegram.
In the format of the telegram emanating from the CCS, reference data of the CCS, which first received the telegram, is generated. The reference data includes: the index of the central communication center where the telegram was first received, the operational number of the channel through which the telegram was received by the central communication system, the serial number, the date of reception, the time of reception. After the end of telegram sign, the CCS indicates the time of its transmission to the OP. In the subheading, before the end, the number of receptions is indicated. Each CKS through which the telegram passes adds 1.
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Processing telegrams in the central communication center
Receiving messages. Consecutive telegraph symbols entering the system from communication channels in the MTK-2 code are converted into telegraph characters, which are accumulated in individual accumulation registers. Signs are formed by scanning the middle part of the parcels. The interface equipment, using a multiplex channel, transmits characters in parallel code to RAM (2 buffers). The buffers work alternately: while one is being filled, the other is processing orders. Each character in the buffer is allocated a cell (2 bytes). From the characters received in the buffer, message blocks of 59 characters each are formed.
The SCS ends receiving the message when it receives end-of-message symbols.
^ Message processing. After receiving the end of the pre-header, the pre-header is analyzed by format and content in accordance with the algorithm. If distortions are detected, the SCS does not accept the message further, cancels the received part and issues a service notification to the communication channel.
Each message in RAM is allocated a row in the message table, equal to 32 bytes. All necessary data for processing is recorded in it: channel number, routing index, message length, its address in RAM.
In accordance with the routing index, the message is queued in the delivery direction.
^ Compilation of archives of telegraph messages. Archives of telegraph messages are compiled to ensure automatic repetition of texts and the latest telegrams and storage of telegram texts for a certain time.
The SKS provides a current archive of telegram texts, as well as a stored archive.
After receiving each message, each message is assigned a station number, and the message is recorded on the NMD. Telegrams transmitted to communication channels remain until it is filled. Then the contents of the current archive are rewritten to NML. The magnetic tape removed from the NML is stored for a specified time in the KSS.
^ Messaging. Before the message is directly issued from the SCS, it is prepared for delivery. It is carried out for the first message in the queue if there is a free channel. Preparation for issuance includes:
reading it from the NMD,
generation of official notices,
formation of the pre-heading and end marks of the telegram,
preparing the necessary information for sending characters to the output buffer.
^ Information security measures. The safety of the information available in the SCS is determined by the reliable operation of the station. Reliable operation of the station depends on the trouble-free operation of the equipment and the ability of the station to remain operational during failures and overloads.
Reliable operation of the equipment is ensured by the presence of 2 branches and corresponding software.
Special measures for the safety of information include:
application of a method for tracking the numbering sequence of all messages;
availability of an additional intracenter number;
protection of switching tables and other arrays from damage.
Questions for self-control
List the main operational and technical characteristics of the CFB.
What is the difference between parallel and split load modes?
Explain the functional diagram of the CFB
Outline the main stages of processing telegrams in the CKS.
Explain the block diagram of the computer complex.
Algorithm for interaction with the end point, with the circuit switching network, DSS-DSS.
Explain the format of the message when transferred from the OP to the CKS.
SECTION 5
Channel-forming telegraph equipment
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Topic 5.1 Construction of equipment for the formation of telecommunication channels
General information about channel-forming equipment
Channel-forming equipment is technical means that make it possible to use a standard PM channel to organize several telegraph communications. Telegraphy in this case is called tonal. On the receiving side, one message is separated from another either due to the fact that the messages occupy different settings in the frequency band 0.3 - 3.4 kHz - FRC, or because they arrive at different times - TRC.
Equipment with VRK type TT-12, T-48, TT-144, equipment with VRK type TVU-12M, TVU-15, DATA, DUMKA.
In equipment with PDM, the channels formed in the PM band are numbered. The number of each channel consists of 3 digits: the first indicates the type of channel (1-50 baud channels, 2-100 baud, 4-200 baud), the next 2 digits indicate the serial number of the channel from the lower limit of the frequency band 0.3 kHz to upper 3.4 kHz. Thus, the 50 baud tone channels are numbered 101-124 / 24 TT channels in the standard TC channel); with a speed of 100 baud they have numbers 201-212; at 200 baud – 401-406.
In equipment with VRC, the main elements are a multiplexer and a UPS signal conversion device. The multiplexer combines telegraph signals coming from different sources into a single digital stream during transmission and distributes this stream to the corresponding receivers at the reception. The UPS matches the parameters of the digital stream with the parameters of the transmission channel.
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Topic 5.2 Channel-forming equipment with frequency division of channels.
Technical data TT – 144
The TT-144 equipment is used to organize low-speed channels on the backbone sections of the telegraph network and data transmission network. The TT-144 voice-frequency telegraphy equipment allows organizing up to 144 two-way discrete channels in the frequency band of the TC channel of cable, overhead and radio relay communication lines. The equipment uses frequency division and frequency modulation. In one HF channel, the equipment allows you to organize the following number of discrete channels: 24 with a speed of 50 Baud, or 12 with a speed of 100 Baud, or 6 with a speed of 200 Baud, or 1 with a speed of 1200 Baud and 6 with a speed of 50 Baud (or 2 with a speed of 200 Baud). The numbering of channels, carrier frequencies, the distance between them and the frequency deviation" in the linear spectrum of the PM channel comply with the requirements of GOST and the recommendations of the CCITT. The equipment also makes it possible to organize mixed different-speed groups of channels in the PM channel.
The equipment uses the principle of individual-group conversion. The group of channels occupying the frequency band 3.6...5.01 kHz was taken as the initial one. For conversion, group carriers with frequencies of 5.4 and 6.84 kHz are used. The equipment can be connected to telegraph devices, equipment and subscriber data transmission kits, switching telegraph stations operating in bipolar bursts with a voltage of ±(5 ... 25) V. In TT channels under normal operating conditions, edge distortions do not exceed 5%. The input and output impedances of the CT channels are 1000 Ohms.
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Block diagram of TT-144 equipment
The block diagram of the TT-144 equipment contains the main blocks: RNG frequency grid generator blocks, interface blocks C, linear equipment blocks LO, channel blocks K, dominance compensator block KP, power supplies. In addition, there are a number of auxiliary blocks.
The frequency grid generator is designed to generate the entire set of highly stable frequencies necessary for the functioning of equipment components. It consists of a block of reference frequency frequencies. block of group frequencies HF. blocks of linear frequencies LC, blocks of shapers F. The block OC contains a quartz oscillator and provides the formation of periodic pulse oscillations with a frequency of 3,932,160 Hz for the operation of the remaining RNG blocks. To generate 21 linear frequencies, there are seven identical blocks LC1-LC7. To change the linear frequencies of the channels, the LF outputs are connected to the channel blocks through the LF linear frequency switching board. The HF block is designed to generate oscillations of carrier frequencies (5.40 and 6.84 kHz) of group converters and a frequency of 2.7 kHz to control the CFP. Frequency modulators and demodulators of blocks K are provided with the necessary frequencies using two blocks F, each containing five shapers that perform the functions of power amplifiers.
The LO block is designed to coordinate the PM channel with individual equipment of TT channels in terms of frequency spectrum, levels and resistance, as well as to signal an understatement of the level in the PM channel. It consists of transmitting and receiving parts, each of which has two signal conversion paths, with a conversion frequency of 5.4 kHz (group A) and 6.84 Hz (group B). The block contains group spectrum converters P, amplifiers Ус and low-pass filters. In group low-pass filters, transmissions are delayed from entering the PM channel by harmonic components from the carrier frequencies and upper sidebands present at the outputs of the phase filter. In the group low-pass filters of the receiving part, the spectrum of the group signal is limited to eliminate the influence of the multiband PPC.
In the group amplifier of the receiving part of the LO block, a stepped AGC is used. When the group signal level is reduced by 9 dB, the gain of the group amplifier increases stepwise by 9 dB. The interface device C is individual equipment designed to convert signals coming from local telegraph circuits (voltage and current) into the signals necessary for the operation of the K channel unit (at transmission), and the reverse conversion (at reception). One block C houses three interface devices, each of which consists of an input and output device. Interface devices are universal and are used for all information transmission rates provided in the equipment.
In the universal block K, DC telegraph messages are converted into frequency-modulated signals in transmission and frequency-modulated signals into telegraph messages in reception. The block consists of a transmitter and a receiver, and all its nodes are located on two boards: on one KFP per and KFP pr, and on the other the remaining devices. Block K, using soldering, can be switched to one of three modes to operate at a nominal speed of 50, 100 and 200 baud/Frequency modulators and frequency detectors of the block operate in all modes at an average frequency of 2.7 kHz.
The transmitter of the universal channel block consists of the following main components: an FM frequency modulator, an additional transmission filter (not shown in the figure) and a switched transmission filter-converter KFP AC. The FM inputs from the RNG receive pulse sequences that are multiples of the lower characteristic frequency and the difference in characteristic frequencies. Depending on the polarity of the messages coming from the interface device, a lower or upper characteristic frequency is generated at the FM output. In the absence of a telegraph signal at the input of the equipment, the lower characteristic frequency is sent to the FM output.
The additional transmitter filter is a low-pass filter and is designed to retain the odd harmonics of the square wave signal coming from the FM output. The switched filter of the transmit converter is used to retain the spectral components of the FM signal located outside the frequency band allocated to the channel, as well as to move the spectrum of the channel signal CT from an average frequency of 2.7 kHz to a linear frequency of 3.66-.-4.98 kHz, specific for each channel. To do this, a control signal fl is supplied to one of the inputs of the CFP per from the RNG With frequency equal to the required linear frequency of the channel in the group. 
Drawing. Block diagram of TT-144
The receiver of the channel block consists of a CFP pr., an additional reception filter DF pr. amplifier-limiter (CA), and a frequency discriminator BH. LPF. PU threshold device, as well as remote control level detector circuits (DF pr. and remote control are not shown in Fig. 8.34). From the group signal, the CFP pr. selects oscillations of a given CT channel and transfers the spectrum of the selected signal from the linear frequency to the frequency of 2.7 kHz. An additional reception filter delays the odd signal harmonics generated at the output of the CFP, etc. The limiting amplifier used in the equipment is described in detail in § 8.2.1. The frequency discriminator converts the FM signal into a series of pulses, the duration of which depends on the frequency of the input signal; the principle of its operation is similar to the operation of the TT-12 black hole equipment.
The low-pass filter selects a constant component from the pulse sequence at the output of the black hole, the value of which changes linearly as the frequency at the receiver input changes. The channel threshold device is designed to generate rectangular telegraph signals. Bipolar rectangular pulses generated by the PU control the operation of the output device of block C. When the signal level at the receiver input is below the minimum permissible value, the remote control generates a blocking signal that sets the PU to a position that ensures the appearance of a starting message in the local telegraph circuit. From the CP predominance compensator block, the PU also receives a dominance compensation signal generated by the CP when the frequency shifts in the PM channel. The CP block contains a transmitter that produces an unmodulated signal with a frequency of 3.3 kHz, and a receiver similar to the receiver of the TT channel. except that after the black hole the signal is sent not to the control unit, but to the inverting amplifier. At the output of the receiver of this channel, a constant voltage is generated, the value of which is proportional to the frequency shift in the PM channel. This voltage is supplied to the threshold devices of CT receivers of all channels and changes their response thresholds, thus eliminating dominance distortions.
The 1200 baud BC channel block, which is part of the TT-144 equipment and provides, using frequency modulation, the transmission of discrete signals at speeds of up to 1200 baud, differs from other blocks in that it contains an individual quartz oscillator and non-QFPs are used as bandpass filters , and 2,C-filters. Compared to the TT-48 and TT-12 equipment, the TT-144 equipment has expanded the composition of operational devices, which allows reducing the time spent on equipment maintenance. These devices include a test signal sensor DS, a control unit for the voice-frequency channel KCH, an indication unit BI with an intercom, and signaling units BS1 and BS2. The BS2 alarm unit is included in each TT-48 section, all other units are located in the RKS control and alarm row. In the DS, test telegraph signals of the type 1: 1 are generated with speeds of 50, 100, 200 and 1200 Baud, as well as the signals “Pressing +” and “Pressing -”. With the help of BI, operational monitoring is carried out: currents and voltages in local circuits; levels at linear inputs and outputs, as well as at the inputs of the control device; presence of predominance (up to ±10%) at channel outputs. The display unit also allows you to organize telephone conversations during measurements and when the equipment enters into communication. The KFC block is designed to control in the TC channel a decrease in the signal-to-interference ratio (with response limits of 18, 24 and 30 dB) and a shift in the control frequency exceeding the set threshold value of 2, 4, 6, 8 or 10 Hz. Blocks BS1 and BS2 generate signals for turning on emergency and warning alarms. The alarm is triggered when the RNG, power supply units are faulty, fuses are blown, the reception level of any TT channel is underestimated by 18 dB or the reception level in the TC channel is more than 20 dB. A warning alarm is triggered when the overall reception level in the PM channel is lowered by more than 9 dB, the established threshold for monitoring the signal-to-interference ratio is exceeded, or the frequency drift in the telephone channel is exceeded.
Questions for self-control
List the technical characteristics of the TT-144.
Explain the composition and purpose of the channel transmitter.
Explain the composition and purpose of the channel receiver.
Topic 5.3 Channel-forming equipment with time division of channels
Technical data. Block diagram of TVU-15 equipment.
Technical data
Block diagrams of TVU-15 equipment
The block diagram of TVU-15 includes input devices of US blocks (individual station equipment consists of five US blocks, three channels each) that convert bipolar telegraph signals with a voltage of ± 20V into unipolar pulses. These pulses are quantized and combined on a time basis by the transmitter block distributor into a single group HS signal. In addition to information signals in the HS, a synchronization combination and service signals are transmitted (via channel 16). The group signal is encoded according to the law of the bipulse code by the encoder of the transmitter of the bipulse UPS-BI signal conversion device and, after amplification, enters through a linear transformer into the communication line. The operating speed of the transmitter is set by a quartz-stabilized generator of the master pulses of the GZI.
The signal received from the line is fed through a transformer to an active corrector of intersymbol distortions introduced by the communication line with a linear amplifier KLUs. The corrector has two stages of adjustment: coarse, performed by resoldering jumpers before connecting the equipment to the line (based on an approximate estimate of the line length), and fine, performed using two potentiometers and a BI indication unit connected to the KLUs output, after connecting the equipment to the line. The corrected signal is amplified and limited in the OU and enters the phase-locked loop circuit in the GZI. In decoder D, using the clock frequency restored by the GZI, the received bipulse signal is decoded into a binary single-pole signal GSD and demultiplexed in the reception distributor of the Pr block. From the Pr outputs, information signals of individual channels are sent to the electronic relays of the US units. The cyclic phasing and control unit of the DFC finds a synchronization combination in the HS and establishes the in-phase operation of the receiving distributor with the transmission distributor. Besides. The DSC processes the information of the control channel, through which test signals are transmitted, allowing for ongoing monitoring of the error rate of the linear signal in the path passing from the main station through the intermediate and loop at the second end station.
Drawing. Block diagram of TVU-15
The linear circuits of the equipment are connected to the communication line through reed relays. With their help, linear circuits can be disconnected from the line manually or remotely (using the “Loop” command) and set to the “Forward” position. Commands for remote switching on of loops with the address of the desired regenerator included in the line are generated by the UVSh-S station loop switching device. Reception of these commands in regenerators is carried out by UVSh-R blocks.
TVU-15B stations differ from TVU-15A only in that instead of US blocks they include station semi-sets of subscriber devices URDC-S and UPDL-S. Separation filters for telephone and telegraph channels URDC-S (made on LC elements) are included as part of BRF blocks placed on the hinged rear covers of TVU-15BN stations or in separate floors of TVU-15SU racks. This allows you to repair TVU-15B stations without disrupting telephone communications.
Monitoring of currents and voltages in local telegraph circuits, supply voltages, distortions of telegraph signals such as predominance, control of signals in symmetrical linear circuits of equipment is carried out using the BI unit. The BI also includes telegraph signal sensors Questions for self-control
List the technical characteristics of TVU-15.
Explain the design features of the transmitter.
Explain the features of transmitter construction
SECTION 6
Networks and data services
Topic 6.1 Organization of a radio packet data network
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Characteristics and structure of the radio packet PD network. Purpose and main functions of network elements.
Data transmission over a radio channel is in many cases more reliable and cheaper than transmission over dial-up or leased channels, and especially through cellular communication networks. In situations characterized by the lack of a developed communications infrastructure, the use of radio means for data transmission is often the only reasonable option for organizing communications. A data transmission network using radio modems can be quickly deployed in almost any geographic region. Depending on the transceivers (radio stations) used, such a network can serve its subscribers in an area with a radius of several to tens and even hundreds of kilometers. Radio modems have enormous practical value where it is necessary to transmit small amounts of information (documents, certificates, questionnaires, telemetry, answers to database queries, etc.).
Radio modems are often called packet controllers due to the fact that they include a specialized controller that implements the functions of exchanging data with a computer, managing frame formatting procedures and accessing a common radio channel in accordance with the implemented multiple access method.
Algorithms for the operation of packet radio networks are regulated by Recommendation AX.25. Recommendation AX.25 establishes a unified packet exchange protocol, i.e. a mandatory procedure for all users of packet radio networks to exchange data. The AX.25 standard is a version of the X.25 standard specially redesigned for packet radio networks.
The peculiarity of packet radio networks is that the same radio channel is used to transmit data by all network users in multiple access mode. The AX.25 exchange protocol provides for multiple access to the communication channel with occupancy control. All users (stations) of the network are considered equal. Before starting transmission, the radio modem checks whether the channel is free or not. If the channel is busy, then the transmission of its data by the radio modem is postponed until it is released. If the radio modem finds the channel free, it immediately begins transmitting its information. Obviously, at the same moment, any other user of this radio network can start transmitting. In this case, the signals of two radio modems overlap (conflict), as a result of which their data is highly likely to be seriously distorted due to mutual interference. The transmitting radio modem becomes aware of this by receiving negative acknowledgments for the transmitted data packet from the receiving radio modem or as a result of exceeding the timeout time. In such a situation, he will be obliged to repeat the transmission of this packet according to the already described algorithm. In packet communication, information in a channel is transmitted in the form of separate blocks - frames. Basically, their format corresponds to the frame format of the well-known HDLC protocol.
A typical packet communication station includes a computer (usually a portable notebook type), a radio modem itself (TNC), a VHF or HF transceiver (radio station). The computer interacts with the radio modem through one of the well-known DTE - DCE interfaces. The RS-232 serial interface is almost always used. The data transmitted from the computer to the radio modem can be either a command or information intended for transmission over a radio channel. In the first case, the command is decoded and executed, in the second, a frame is formed in accordance with the AX.25 protocol. Before direct transmission of a frame, the sequence of its bits is encoded with a linear code without returning to zero NRZ-I (Non Return to ZeroInverted). According to the NRZ-I coding rules, a drop in the physical level of the signal occurs when a zero is encountered in the original data sequence.
A packet radio modem is a combination of two devices: the modem itself and the TNC controller itself. The controller and modem are connected by four lines: ТхD - for transmitting frames in the NRZ-I code, RxD - for receiving frames from the modem also in the NRZ-I code, PTT - for sending a signal to turn on the modulator and DCD - to send a channel busy signal from the modem to the controller. Typically, the modem and packet controller are constructed in the same housing. This is the reason why packet radio modems are called TNC controllers.
Before transmitting the frame, the controller turns on the modem using a signal via the PTT line, and sends the frame in the NRZ-I code via the TxD line. The modem modulates the received sequence in accordance with the accepted modulation method. The modulated signal from the modulator output is fed to the microphone input MIC of the transmitter.
When receiving frames, a carrier modulated by a sequence of pulses is supplied from the EAR output of the radio receiver to the input of the demodulator. From the demodulator, the received frame in the form of a sequence of pulses in the NRZ-I code enters the packet radio modem controller.
Simultaneously with the appearance of a signal in the channel, a special detector is triggered in the modem, producing a channel busy signal at its output. The PTT signal, in addition to turning on the modulator, also performs the function of switching the transmit power. It is usually implemented using a transistor switch that switches the transceiver from receiving mode to transmitting mode.
In packet radio communications based on standard radio stations, two modulation methods are used for short and ultrashort waves. HF uses single-sideband modulation to form a voice-frequency channel in a radio channel. For data transmission, frequency modulation of the subcarrier is used in the telephone channel frequency band 0.3 to 3.4 kHz. The subcarrier frequency can be different, and the frequency spacing is always 200 Hz. In this mode, a transmission speed of 300 bps is provided. In Europe, the frequency typically used is 1850 Hz for transmitting "0" and 1650 Hz for transmitting "1".
In the VHF band, they often operate at a speed of 1200 bps when using frequency modulation with a subcarrier frequency spacing of 1000 Hz. It is accepted that “0” corresponds to a frequency of 1200 Hz, and “1” to 2200 Hz. Less commonly, relative phase modulation (RPM) is used in the VHF band. In this case, transmission speeds of 2400, 4800, and sometimes 9600 and 19200 bps are achieved.
Questions for self-control
Describe the structure of the radio packet data transmission network.
What is included in a packet communication station.
Explain the use of radio modems.
Purpose of networks DIONYSUS, REX - 400. Services provided. Composition of network equipment. INTERNET network. Protocols, basic services, subscriber access.
^ INTERNET network
The Internet is a worldwide computer network, which is a unified information environment and allows you to obtain information at any time. But on the other hand, the Internet contains a lot of useful information, but searching for it requires a lot of time. This problem gave rise to the emergence of search engines.
An information system is an organized set of software, hardware and other auxiliary tools, technological processes and functionally defined groups of workers that ensure the collection, presentation and accumulation of information resources in a certain subject area, searching and issuing information necessary to meet the information needs of users. Information systems are the main means, tools for solving problems of information support for various types of activities and the most rapidly developing branch of the information technology industry.
The World Wide Web or WWW for short is the name of the most widespread Internet application today, built on the use of hypertext. A hypertext document in computer execution is a file (text, graphic image and any other piece of information) that has links to other files (documents) in its structure. To connect to the World Wide Web you need a computer with a modem connected to the Internet. An Internet browser program must be installed on your computer: Microsoft Internet Explorer or Netscape Communicator. After your computer connects to the Internet, in the command line you should write the address of the information that you need to display on your computer.
^
The concept of information retrieval systems
An automated search system is a system consisting of personnel and a set of automation tools for its activities, implementing information technology to perform established functions.
An information system is understood as an organized set of software, hardware and other auxiliary tools, technological processes and functionally defined groups of workers that ensure the collection, presentation and accumulation of information resources in a certain subject area, the search and provision of information necessary to meet the information needs of an established user population. – system subscribers.
In the work, the search process is presented in four stages: formulation (occurs before the search begins); action (starting search); overview of results (the result that the user sees after searching); and refinement (after reviewing the results and before returning to the search with a different formulation of the same need).
There are three “pillars” of search indexes in Russia today. This is Rambler ( www.rambler. ru), "Yandex" ( www.yandex. ru) and “Aport2000” ( www.aport. ru).
^ Internet protocols
The Internet Protocol (IP) implements the distribution of information over an IP network. The IP protocol transfers information from node to network node in the form of discrete blocks - packets. At the same time, the IP protocol is not responsible for the reliability of information delivery, the integrity or preservation of the order of the packet flow, and does not solve the problem of information transfer with the quality required for applications; two other protocols solve it:
TCP – Transmission Control Protocol
UDP is a datagram protocol that sits above IP, using IP procedures to transfer information.
The UDP protocol is a datagram protocol, according to which each block of transmitted information (packet) is processed and distributed from node to node as an independent unit of information - a datagram.
The functions of the IP protocol are performed by “host” computers connected to a single Internet network, operating using the IP protocol, which is connected using routers in physical networks: local networks operating under hardware-dependent protocols (Internet), or communication systems of any physical nature (modem or dial-up or leased lines, X.25, ATM, Frame Relay networks).
^
Email Definition
Nowadays the email system is becoming more and more popular.
E-mail - exchange of postal messages with any Internet subscriber. It is possible to send both text and binary files. The following limitation is imposed on the size of an email message on the Internet - the size of an email message should not exceed 64 kilobytes.
Email is similar to regular mail in many ways. With its help, a letter - a text provided with a standard header (envelope) - is delivered to a specified address, which determines the location of the machine and the name of the addressee, and is placed in a file called the addressee's mailbox, so that the addressee can get it and read it at a convenient time . At the same time, there is an agreement between email programs on different machines on how to write the address so that everyone understands it.
The reliability of email greatly depends on what email programs are used, how far away the sender and recipient of the email are from each other, and especially on whether they are on the same network or on different ones. This is the most popular use of the Internet in our country today. Estimates say that there are over 50 million email users in the world. In general, in the world, email traffic (smtp protocol) takes up only 3.7% of the total network traffic. Its popularity is explained both by pressing requirements and by the fact that most connections are “on-call access” class connections (from a modem), and in Russia, in general, in the vast majority of cases, UUCP access is used. E-mail is available with any type of Internet access.
E-mail (Electronic mail) - electronic mail (common - an electronic analogue of regular mail. With its help, you can send messages, receive them in your electronic mailbox, respond to letters from your correspondents automatically, using their addresses, based on their letters, send copies of your letter to several recipients at once, forward a received letter to another address, use logical names instead of addresses (numeric or domain names), create several mailbox subsections for various types of correspondence, include text files in letters, use the “mail reflector” system for conducting discussions with a group of your correspondents, etc. From the Internet, you can send mail to adjacent networks if you know the address of the corresponding gateway, the format of its requests and the address in that network.
Using e-mail, you can use fttp asynchronously. There are many servers that support such services. You send an e-mail to the address of such a service containing a command from this system, for example, to give a listing to a certain directory, or to send such and such a file to you, and you automatically receive an e-mail response with this listing or the required file. In this mode, it is possible to use almost the entire set of regular ftp commands. There are servers that allow you to receive files via FTP not only from themselves, but from any FTP server that you specify in your e-mail..
E-mail makes it possible to conduct teleconferences and discussions. For this purpose, mail reflectors installed on some node working machines are used. You send a message there with instructions to subscribe you to such and such a reflector (discussion, conference, etc.), and you begin to receive copies of the messages that the discussion participants send there. The mail reflector simply sends copies of emails to all subscribers upon receipt.
^
Addressing in the email system
In order for your email to reach its recipient, it must be formatted in accordance with international standards and have a standardized email address. The generally accepted message format is defined by a document called "Standard for the Format of ARPA - Internet Text messages", abbreviated as Request for Comment or RFC822, and has a header and the message itself. The header looks something like this:
From: postal email address - from whom the message came
To: postal email address - to whom it is addressed
Cc: postal email addresses - who else is sent to
Subject: message subject (free form)
Date: date and time the message was sent
The From: and Date: header lines are usually generated automatically by software. In addition to these header lines, the message may contain others, for example:
Message-Id: unique message identifier assigned to it by the mail machine
Reply-To: usually the address of the subscriber to whom you are replying to the letter sent to you
The message itself is, as a rule, a text file of a fairly arbitrary form.
When transmitting non-text data (executable program, graphic information), message recoding is used, which is performed by appropriate software.
The postal email address can have different formats. The most widely used address generation system is DNS (Domain Name System), used on the Internet. The address is decrypted and translated into the required format by built-in software used in a given email network.
From a logical point of view, in order for an address to be informative, it must contain:
Subscriber ID (by analogy - the TO: line on the mail envelope);
Postal coordinates that determine its location (by analogy - house, street, city, country on a postal envelope).
A postal email address has all these components. In order to separate the subscriber ID from his mail coordinates, the @ icon is used.
A postal email address in Internet format can look like:
In the example under consideration, aspet is the subscriber identifier, usually composed of the initial letters of his last name, first name, patronymic (Anatoly Sergeevich Petrov). What is to the right of the @ sign is called a domain and uniquely describes the location of the subscriber. The components of a domain are separated by dots.
The rightmost part of the domain, as a rule, indicates the recipient's country code - this is the top-level domain. The country code is approved by the international ISO standard. In our case, ru is the code of Russia. However, a network designation can also appear as a top-level domain. For example, in the USA, where there are networks connecting universities or government organizations, the abbreviations edu - Educational institutions, gov - Government institutions and others are used as top-level domains.
^
Mail programs
There are a lot of email programs, many of them are free. They are all quite similar and differ only slightly in their additional capabilities and in the degree of compliance with accepted standards. The most common programs: Microsoft Internet Mai, Microsoft Outlook Express, Netscape Messenger, Eudora.
After configuring your email program, you should find two buttons: one allows you to check your mail, the other allows you to create a new message. Click on the second of them - a new window will appear. Here you fill in the following fields:
^ To: (To)- it goes without saying;
Copy: (Cc:)- other recipients;
Bcc:- to someone else, but so that the main addressee does not know about it;
Subject: (Subject:)- what your letter is about is not required, but highly recommended;
Finally, the large field below those listed above is for the text of the letter itself. You can accompany the text with an application - to do this, find the corresponding button (often indicated by a paper clip), which will allow you to select any file from your hard drive. You can send any files as an attachment: programs, sound files, graphic files, etc. If now, without closing the mail program, you connect to the provider and click on the “Send” button, then your letter will go to the addressee. To get started, you can send a letter to your own address.
Now click on the button that serves to check your mail and you will receive your message back. It will go to your inbox. Each email program, after installation, automatically creates at least three folders: for incoming messages, for outgoing messages - copies of what you send are saved here, and a trash can - deleted messages are temporarily sent here in case you erased them by mistake.
^
Protocols for receiving and transmitting mail
Email programs for personal computers use different protocols for receiving and sending mail. When sending mail, the program interacts with the outgoing mail server, or SMTP server, using the SMTP protocol. When receiving mail, the program interacts with the incoming mail server, or POP3 server, using the POP3 protocol. These can be either different computers or the same computer. You will need to obtain the names of these servers from your ISP. Sometimes a more modern protocol is used to receive mail - IMAP, which allows, in particular, to selectively copy messages received for you from the mail server to your computer. To use this protocol, it must be supported by both your ISP and your email program.
^ Simple Mail Transfer Protocol (SMTP)
Interaction within SMTP is based on the principle of two-way communication, which is established between the sender and recipient of an email message. In this case, the sender initiates the connection and sends requests for service, and the recipient responds to these requests. In fact, the sender acts as a client, and the recipient acts as a server. 
Drawing. SMTP protocol interaction scheme
The communication channel is established directly between the sender and recipient of the message. With this interaction, mail reaches the subscriber within a few seconds after sending.
^
Mail Delivery Protocol (POP)
Post Office Protocol (POP) is a protocol for delivering mail to a user from a mailbox. Many of the concepts, principles, and concepts of POP are similar to SMTP. POP commands are almost identical to SMTP commands, differing in some details.
The design of the POP3 protocol allows the user to log in and check out the backlog of mail, rather than having to first log into the network. The user accesses the POP server from any system on the Internet. At the same time, he must launch a special mail agent (UA) that understands the POP3 protocol. At the head of the POP model is a separate personal computer that operates solely as a client for the mail system. Under this model, the personal computer neither delivers nor authorizes messages to others. Also, messages are delivered to the client using the POP protocol, but are still sent using SMTP. That is, on the user’s computer there are two separate agent interfaces to the mail system - delivery (POP) and sending (SMTP). The developers of the POP3 protocol call this situation “split agents” (split UA).
The POP3 protocol specifies three stages in the process of receiving mail: authorization, transaction, and update. After the POP3 server and client have established a connection, the authorization stage begins. At the authorization stage, the client identifies itself to the server. If authorization is successful, the server opens the client's mailbox and the transaction stage begins. In it, the client either requests information from the server (for example, a list of mail messages) or asks it to perform a certain action (for example, issue a mail message). Finally, during the update phase, the communication session ends. In table Table 7 lists the POP3 protocol commands that are required for a minimal configuration implementation running on the Internet.
The POP3 protocol defines several commands, but only two responses are given to them: +OK (positive, similar to the ACK confirmation message) and -ERR (negative, similar to the “not acknowledged” NAK message). Both responses confirm that the server has been contacted and that it is responding to commands at all. As a rule, each answer is followed by a meaningful verbal description of it.
^ External gateways of the DIONYSUS center
Within the framework of DIONIS technology, the following are implemented: multi-purpose (fax+telegraph+telex) gateway, X.400 gateway, UUCP gateway. External gateways serve for automatic exchange of information between DIONIS hosts and other networks, providing transportation and necessary data conversion.
The set of gateways of DIONYSUS centers may differ from those shown in the figure; there may be no external gateways at all.
The figure shows an option for connecting the host computer of the DIONIS system with external gateways via a local network. In fact, there are many ways to make this connection. As a means of physical communication between the DIONIS host computer and external gateways, you can use:
- local network;
direct port-to-port connection via cable (“null modem”);
dial-up or dedicated telephone line (with modem);
packet switching network.
The functions of external gateways cannot be implemented on the host computer of the DIONIS system, however, one gateway computer can implement the functions of 2 main gateways, providing interaction with fax and telegraph-telex networks; such a gateway computer is called a multifunctional gateway.
At the same time, the multifunctional gateway can serve:
up to 6 fax channels;
up to 16 telegraph-telex channels;
up to 8 virtual channels of data exchange with DIONIS systems and/or other multifunctional gateways.
The X.400 gateway and UUCP gateway are always installed on separate computers. The UUCP gateway ensures the exchange of messages between DIONIS subscribers and networks that use the UUCP mail forwarding protocol for forwarding. In Russia, the widely used RELCOM network belongs to this type.
Data exchange via the UUCP protocol is carried out in batch mode, so the connection between the gateway computer and the corresponding UUCP resource is carried out through one dial-up telephone channel using an asynchronous modem.
The functions of a UUCP gateway can be performed by any IBM-compatible PC (including XT), which has at least two serial ports and a hard drive sufficient to accommodate transmitted and received information,
The X.400 gateway is implemented on a separate computer with an Intel 80386 processor or higher, equipped with an intelligent controller that implements the X.25 protocol and lower levels of the X.400 protocol. The gateway is designed for information communication with mail systems operating in accordance with the X.400 protocol. Due to the high cost of the intelligent controller and software for implementing the X.400 protocol, as well as due to the small distribution of this protocol for data transmission, corporate networks can, without harm to their subscribers, use the X.400 gateways of existing commercial networks with which they will communicate any other type (for example, inter-host communication of DIONIS technology, as well as communication via UUCP protocols using an external gateway or via SMTP protocol without an external gateway). It is almost always possible to receive and send information in accordance with the X.400 protocol without having your own X.400 gateway.
Fax gateway (FS) DIONIS is designed to organize the exchange of information between subscribers of DIONIS systems (and other e-mail systems) and owners of fax machines. A network of FS installed in different cities can significantly increase the reliability of fax communications compared to the usual transfer of information between two fax machines. This is achieved by the fact that the FS subscriber must call the FS in his city by phone, and the transfer of fax messages between cities is provided by DIONIS or FS nodes, interconnected by dedicated channels of data transmission networks.
DIONIS technology fax gateways provide the following basic services.
In the fax sending mode, the FSC receives information from the DIONIS host computer in the form of letters or files, converts them into fax format, dials the recipients' fax machines and sends fax messages, providing users with the following services:
sending text messages to subscribers' fax machines;
multiple distribution of one message to any number of fax machines of subscribers;
placement of registered graphics anywhere in the text message being sent
- brand name, signature, seal, etc.;
if the DIONYSUS center has its own fax gateway, then subscribers of this center are given the opportunity to include any (and not just pre-registered) graphic images in a text message.
If multi-channel FS is implemented, i.e. If it is necessary to service more than one fax channel, then a high-speed four-port 4*RS232-FIFO card is used to connect fax modems.
Along with their use in data networks, FS can be used autonomously to create specialized fax networks designed to serve only clients using fax machines and/or fax modems. A distinctive feature of such networks is the increased quality of fax transmission, as well as a significantly wider range of services:
Receiving faxes at the initiative of the recipient;
Creation of reference and information fax systems, etc.
The telegraph-telex gateway (TT gateway) is designed to organize the exchange of information between subscribers of DIONIS nodes (and other email systems) and owners of telegraph and telex devices.
Telegraph and telex networks differ in the addressing system they use and have different tariffs. In addition, the telex network is an international network, so only letters of the Latin alphabet are allowed to be used in it (although when exchanging telexes between Russian subscribers, Cyrillic is also allowed). However, from a technical point of view, the telegraph network (AT-50) and the telex network (Intelex) are identical. Therefore, all further presentation applies equally to telex and telegraph.
A hardware multi-channel TT gateway can be implemented on the basis of any IBM-compatible personal computer of the AT-386 class or higher. It is possible to implement a TT gateway on a multifunctional gateway. The low speed of data exchange over telegraph channels allows one gateway computer to provide simultaneous operation on 16 lines at once. Connection to telegraph lines is carried out through 1- or 2-port telegraph-telex adapters connected to the RS232 ports of the TT gateway computer. If more than two adapters are connected, then an additional RS232 controller for 4 or 8 ports is required for the gateway computer.
Using a telegraph-telex gateway, a DIONIS subscriber can send a message to the recipient’s telegraph device and vice versa - receive information sent from the telegraph device by e-mail.
To solve the problem of exchanging messages between subscribers of telegraph and telex networks, the TT gateway can be used autonomously.
^ Working in the DIONYSUS network
When working in the DIONIS network, in the Internet-name of the gateway column, the address of the telex (telegraph) gateway accepted on the Internet is specified. It is to the address indicated in the Internet-name of the gateway that users of the external gateway DIONIS send their telex (telegraph) messages via email, intended for sending to subscribers of the TELEX network (AT-50). In the case when the external gateway is not installed locally and the Internet name of the telex (telegraph) gateway is specified, then the telex (telegraph) gateway provides the following possibilities for its use: 1) the telex (telegraph) gateway can be used (send and receive telex (telegraph) messages through it ) messages) subscribers of the associated host DIONYSUS; 2) the telex (telegraph) gateway can be accessed by any external subscribers who have access to Internet addressing, i.e.
email users from almost all existing networks, because... Almost any network either directly supports IRS822 addresses or has gateways with a network that supports them. (It should be noted that for this it is also necessary that the DIONIS host associated with the external gateway be connected to some network and included in its routing tables. Otherwise, only subscribers associated with the external gateway will have access to the telex (telegraph) gateway hosta DIONYSUS); 3) Users - owners of telex and telegraph devices, i.e. Users working with the gateway via telex (telegraph) channels are able to exchange information (send and receive letters) with email subscribers. Users - owners of telex and telegraph devices can use the services of a fax gateway (send fax messages)
Questions for self-control
1. Purpose of the Internet. Network protocols.
2. E-mail - electronic mail. Purpose, basic concepts.
3.Addressing in the email system
4. Describe the protocols for receiving and transmitting mail
5.Explain the purpose of the DIONYSUS network.
6.Give an example of how the DIONIS gateway works.
Topic 6.3 Security methods in data services
Peculiarities of coding in data transmission services. Use of redundant codes.
^
Error protection methods
Errors that may occur during the transmission and processing of information are standardized by quantity and compliance with these standards is a prerequisite. Most errors appear during the procurement and transmission process. Therefore, it is necessary to introduce an RCD into the equipment, which can be in the transmitting and receiving parts of the device. The RCD must provide:
1) error detection; in this case, the location of the error is determined within the code combination or group of combinations.
2) correction of the detected error.
What is common to all methods and RCDs is that redundancy is introduced into the transmitted data, i.e. Along with the information that needs to be transmitted to the consumer, additional service information is transmitted over the channel, the task of which is to ensure the required transmission fidelity. Redundant information is generated and processed by the equipment itself and is not delivered to the consumer. Redundant information includes:
1)Additional elements of the code combination that are entered by the VDU of the transmitting part; The receiving VDU detects the error and determines its location. Such additional elements are called verification elements.
2) Service code combinations that are exchanged between transmitting and receiving RCDs at the time of error detection and correction.
3) information transmitted repeatedly to correct previously transmitted data in which errors were detected.
During normal operation of the communication channel, the check elements of the code combination have the greatest redundancy, because check elements are constantly present, and service combinations and repetitions are transmitted only as needed, i.e. when an error is detected.
With any detection method, some errors remain undetected and uncorrected. Information containing undetected errors is displayed to the consumer and may distort the results. Therefore, the most important characteristic of an RCD is the error detection rate.
Kobn=L/M,
Where L is the number of detected errors;
M is the total number of errors per measurement session.
The number of undetected errors, as well as the error detection rate, depends on two factors:
1) characteristics of errors occurring in the channel;
2) the redundancy of the RCD introduced into the transmitted information, and first of all - from the number of test digits in the code combination.
The greater the redundancy, the greater the number of errors that will be detected in the receiving RCD. But an increase in redundancy leads to a decrease in the amount of useful information, i.e. to a decrease in the throughput of the communication channel, therefore, another characteristic of the RCD is the redundancy coefficient R, which shows at what redundancy a given increase in fidelity is achieved.
R=n/m=(m + k)/m,
Where n is the total number of elements of the code combination;
M is the number of information elements;
K is the number of check elements.
^
Classification of ways to increase fidelity
Drawing. Classification of ways to increase fidelity
All known methods of increasing fidelity can be divided into two groups: without feedback and with feedback.Feedback is a reverse channel through which service interaction signals are transmitted from the receiving ADF to the transmitting one. The scope of application without an OS is limited, because with PD, two-way channels are used, allowing transmission in the forward and reverse directions. The most efficient systems are those with an OS. Via the OS channel, the transmitting ADF receives information about errors detected in the receiving ADF. With this information, the transmit ADF can be adjusted depending on the amount of reception, i.e. change transmission redundancy depending on the presence and number of receive errors. If there are currently no errors, the redundancy introduced by the transmit ADF into the original information will be minimal and throughput will be maximized. When errors occur, transmission redundancy increases to ensure the specified PD accuracy. Those. the presence of the OS allows you to automatically adjust the transmission redundancy depending on the transmission amount of work of the communication channel. The return channel is used not only to transmit error information, but also to transmit the reverse data stream.
^
Systems without feedback
In systems without an OS, increasing fidelity can be achieved in two ways: multiple transmissions and using error-correcting codes.
In multiple transmission, each code combination is transmitted several times. In the receiving RCD, all accepted combinations are compared element by element. If the elements of the same name in all combinations coincide, the RCD concludes that there are no errors, and the accepted sign is displayed to the consumer. If the combinations do not match, an error is detected, but the system does not correct it.
A second method of multiple transmission is possible - a system with parallel transmission. The same code combination is transmitted simultaneously over several channels from the transmitting to the receiving ADF. At reception, the RCD analyzes the received combinations of error detection and correction in the same way as in a system with multiple transmissions. The disadvantage is a lot of redundancy.
Another method is based on the use of special codes that automatically correct errors. These codes allow the receiving RCD, in the event of an error, not only to detect it, but also to determine which elements of the combination were received incorrectly.
Then the RCD changes the significant positions of these elements to the opposite ones (1 to 0, 0 to 1). The corrected code combination is displayed to the consumer. These systems are complex and expensive, and there is a lot of redundancy.
^
Feedback systems
The most widespread are SPs with information feedback IOS and decisive feedback ROS. Correction of detected errors is carried out by retransmitting technical combinations in which errors were detected.
^
Systems with information feedback IOS
Data transmitted from information sources to its consumer arrives via the forward channel to the ADFpr and is immediately transmitted in full via the reverse channel to the ADFpr. In the SRU comparing device, an element-by-element comparison of all transmitted combinations is carried out with the same combinations arriving via the reverse channel. If all elements of the combination match, the information is considered transmitted without error. If an error is detected, the combination is rejected and the call is repeated. Thus, in the IOS system, decisions about the absence or presence of an error are made not by the receiving part, but by the transmitting part of the ADF.
Advantages: high error detection rate, ability to transmit without additional recoding.
Almost any error is detected in the SRU, with the exception of mirror errors - simultaneous distortion of the combination in the forward and reverse channels, when the error in the forward channel is compensated by an error in the reverse channel. For example:
Transmitted via forward channel 01010
Received on forward channel 00010
Transmitted on reverse channel 00010
Received on reverse channel 01010
The comparison shows a complete match of the combinations, that is, the absence of an error, but the consumer will receive the erroneous combination 00010. The probability of a mirror error is very small.
Disadvantage: a system with IOS is uneconomical in terms of channel capacity, since the reverse channel is constantly busy for transmitting verification and service information.
^
Systems with decision feedback POC
Data
APD PA request APD PB Request
Drawing. Block diagram of a data transmission system with IOS
Systems with POC allow transmission over a two-way channel simultaneously in both directions, while protecting both channels of information from errors. Error detection is carried out in the receiving part of the ADF. Error correction – when retransmitting incorrectly received information. Points A and B simultaneously transmit data from the AI to the PI. In the receiving part of the ADF, the accuracy of the received combination is monitored. When an error is detected, the ADF sends a request signal to the opposite point via the same channel as the data. Having received the request signal, the opposite ADF pauses data transmission and repeats that part of the information in which it detects errors. Received data is also checked and, if there is no error, displayed to the consumer. To check for error-free data, the data coming from the AI is re-encoded in the transmitter with a redundant code that allows errors to be detected.
The redundancy created by check code elements is relatively small, and therefore ensures high efficiency in the use of channels. A decrease in transmission quality can occur not only due to undetected errors, but also due to insertions and omissions of information. An insertion occurs when one of the combinations of transmitted data, due to an error, turns into a service combination of the request. The ADF receiving this false request repeats the last combination. As a result, the PI will receive the same combination twice, which is equivalent to an error. The condition for a drop is the transformation of the request combination into any other combination. In this case, the detected error is not corrected, since retransmission does not occur. It is erased in the receiver and the consumer will not receive this combination.
Questions for self-control
List security methods in data services.
Why is redundancy introduced?
What data is included in redundant information?
What determines the number of undetected errors?
List ways to increase fidelity without feedback.
The principle of operation of systems with information feedback.
The principle of operation of systems with decisive feedback.
Kopnichev L.N., Sakharchuk S.I. Telegraphy and terminal equipment for documentary communications. – M.: Radio and communication, 1999.
Tarnopolsky I.L. , Tarnopolsky V.L. Electrician of telegraph communication station equipment – M.: Radio and Communications, 2000.
Pavlova G.F. Basics of telegraphy, - M.: Radio and Communications, 1999.
Steklov V.K. Telegraphy and data transmission systems. - M.: Radio and communication, 1999.
Krug B.I., Popantonopulo V.N., Shuvalov V.P. Telecommunication systems and networks T.1 – Novosibirsk: Nauka, 1999.
general characteristics
Telephone exchange is a set of technical means designed for switching communication channels of a telephone network. At the telephone exchange, certain telephone channels are connected - subscriber and trunk lines - for the duration of telephone conversations and are disconnected at the end of the negotiations; For this purpose, the streams of telephone messages are combined and distributed across communication lines. A telephone exchange is a type of communication center. Typically, a telephone exchange is located in a special building.
According to the switching method, telephone exchanges are divided into manual (RTS) and automatic (PBX). RTS is equipped with telephone switches; Channel switching is performed by a telephone operator.
PBX - automatic telephone exchange - is a special device with the help of which a call signal is automatically transmitted between two or more telephone sets, while maintaining the ability to establish and disconnect a connection between them. The PBX can work with external telephone networks, such as: GSM, IP networks, city network, and with internal ones, i.e. between themselves. The main task of the PBX is to ensure communication between internal network subscribers and the “outside world”.
Automatic telephone exchanges, depending on the type of switching devices used, are:
Decadal-step - built on electromechanical finders, respectively with machine and electromagnetic drives;
Coordinate, in which multiple coordinate connectors serve as switching devices;
Electronic, for example, with switching via semiconductor devices (such automatic telephone exchanges are under development);
Digital - stations whose operation is based on forwarding via digital signals;
Basic functions of PBX.
The telephone exchange has many useful functions that will help make the work process more efficient, providing high-quality multi-channel communication:
Using an internal line for negotiations without the participation of the landline. that is, during a conversation between participants in the internal PBX network, the city incoming line remains free;
Possibility of simultaneous conversation between internal and city network subscribers - conference calls;
Automatic search for a free line to make an external call;
Notification about the release of a city line;
Ability to use auto-dial mode and call forwarding;
"Director - Secretary" mode;
Establishing telephone numbers that will receive external calls;
Ability to set a different ringer for all types of calls;
Possibility to set bans on long-distance calls and some landline numbers;
Remote listening of premises;
Possibility of connecting an answering machine, fax, modem;
Controlling the operation of the telephone exchange via a computer.
The possibilities of a modern PBX are almost limitless; it allows you to expand the number of incoming lines and internal subscribers. The expansion is available thanks to the modular principle of building the PBX, i.e. All you need to do is install an additional expansion card. This opportunity significantly reduces costs, because purchasing a new PBX requires significant costs, including its installation.
Composition and operating principle of automatic telephone exchange.
The ATS includes:
1) switching system and control devices;
2) input devices for connecting telephone communication lines to the switching system;
3) installation of electrical power;
4) auxiliary devices (ventilation, heating, etc.).
The switching system (CS) and control devices (CU) are usually located in the machine room.
PBXs are located in rooms called cross-country. In the crossover, consisting of a subscriber crossover and a crossover of connecting lines, inputs are concentrated, as well as means of electrical protection of station devices from influence from the lines. In the glove room, main (subscriber) communication cables and cables of high-capacity connecting lines are divided into cables of smaller capacity, convenient for inclusion in cross-connect devices.
Cross equipment.
CROSS- TO switching R distributive ABOUT equipment WITH system WITH connection: It is used to transfer from multi-pair trunk (from a city automatic telephone exchange) or multi-pair cables of subscriber sets to wires going to subscriber telephone sockets at user workplaces. ross are switching distribution equipment for communications. Unified crosses are available in floor and wall versions. The floor design of the cross-connection consists of unified elements (strafes and modules) and allows the formation of cross-countries with one-sided (wall) and two-sided placement of linear and station sides. The number of strafes and modules is determined by the capacity of the cross. The capacity of the crossover is determined in numbers. One number includes a line and station pair and is designed to connect one two-wire line. The capacity is increased by merging cross sections.
The design of the wall cross is unified on the basis of floor-mounted elements. The capacity of the cross-connection, depending on the length of the mounting rails, ranges from 100 to 1000 subscriber and connecting lines with the possibility of expansion. The main elements of the crossover are plinths and service accessories. Plinths are used for connecting cables and cross-connecting wires. The plinths are produced in the following standard sizes: 10x2; 8x2; 5x3 and 8x3 for digital cross.
There are station and main parts of the crossover.
That part of the cross-connect to which all the PBX ports are connected is called the station side.
The part of the cross-connect to which the wires from the subscriber sockets fit is called the main side.
Using the PKSV cross-connect cable and a special tool, these parts of the cross-connect are connected.
This allows you to quickly recross (switch) a pair (landline number, internal number) at the request of subscribers without using the PBX administration program.
Voltage and current lightning protection can be installed on the cross-connect to protect the equipment that is connected to it (telephones, automatic telephone exchanges, etc.)
Fastening elements:
Mounting clamps
19" designs
Cross boxes
Cross racks
Service accessories:
Test cords
Installation tool
Lightning protection elements:
Integrated current and voltage module
Specialized telephone line analyzers.
The equipment of PBX cross-country premises includes test and measuring tables (TMS), designed for operational measurements and testing of subscriber lines, telephone sets, PBX subscriber kits and connecting wires.
IIS equipment for electromechanical stations can be divided into five main parts:
Connecting device for connecting the IIS to the connecting (subscriber) line being tested
Test part for determination
Serviceability of the subscriber line, telephone set and PBX subscriber kit;
Measuring part for operational measurements of electrical parameters of the line and TA on direct current;
Service part for receiving applications and conducting conversations with subscribers and PBX staff;
An intercom for dialing, receiving and transmitting a conversation, used in conjunction with the test and service parts.
Technical capabilities of IIS:
Connecting device.
The connecting device allows you to connect the IIS to the line being tested either using automatic data installation devices, by dialing the number of the unit being tested, or in a cross-connect using test cords. Automatic connection is possible only to subscriber lines, and with the help of cords - to any connecting lines.
Test part.
The testing part of the IIS allows:
Call a subscriber who is on-hook using an inductive current;
Call the subscriber who is off-hook with a phonic signal of increasing volume;
Monitor the progress of connection establishment and conversation on the tested line;
Call the station on the line being tested and dial any number;
Negotiate along the line being tested both towards the line and the station;
Check the quality of the conversational circuits of the telephone by introducing an artificial line with an attenuation of 26 dB into the conversational path during a conversation;
Check the correct operation of the telephone dialer included in the line.
Measuring part.
The measuring part allows:
Measure the ohmic resistance of the subscriber and connecting lines (both two and three wire);
Measure the insulation resistance between wires A and B of the subscriber line, as well as between any wire and ground within the range of 1-10 Ohms;
Check for the presence of foreign polarity on the wires of the line by measuring the insulation resistance between each wire and the minus of the ATS batteries;
Check the integrity of the capacitor in the subscriber's telephone set;
Check the serviceability of the protective fuses of the crossover.
In general, the IIS allows you to check the telephone line for unauthorized connection in all operating modes of the telephone. The latest generation electronic PBXs have a rich set of service functions, so detection of illegal connections is greatly simplified. Naturally, only ATS employees can perform such work.
It seems interesting to use devices designed specifically for information security to monitor the line. From the entire volume of data obtained using such specialized testers, it is necessary to select those that indicate the facts of connecting various devices to the line, line breaks, etc.
Test and measuring table IIS.
Voice-frequency telegraphy equipment TT-144.
The TT-144 telegraphy equipment is made according to the principle of PDK with frequency modulation and is intended for the organization of telegraph channels on the main section. It operates via PM cable, overhead or radio relay communication lines.
Voice-frequency telegraphy equipment TT-144
Channel-forming telegraph equipment
Topic 5.1 Construction of equipment for the formation of telecommunication channels
General information about channel-forming equipment
Channel-forming equipment is technical means that make it possible to use a standard PM channel to organize several telegraph communications. Telegraphy in this case is called tonal. On the receiving side, one message is separated from another either due to the fact that the messages occupy different settings in the frequency band 0.3 - 3.4 kHz - FRC, or because they arrive at different times - TRC.
Equipment with VRK type TT-12, T-48, TT-144, equipment with VRK type TVU-12M, TVU-15, DATA, DUMKA.
In equipment with PDM, the channels formed in the PM band are numbered. The number of each channel consists of 3 digits: the first indicates the type of channel (1-50 baud channels, 2-100 baud, 4-200 baud), the next 2 digits indicate the serial number of the channel from the lower limit of the frequency band 0.3 kHz to upper 3.4 kHz. Thus, the 50 baud tone channels are numbered 101-124 / 24 TT channels in the standard TC channel); with a speed of 100 baud they have numbers 201-212; at 200 baud – 401-406.
In equipment with VRC, the main elements are a multiplexer and a UPS signal conversion device. The multiplexer combines telegraph signals coming from different sources into a single digital stream during transmission and distributes this stream to the corresponding receivers at the reception. The UPS matches the parameters of the digital stream with the parameters of the transmission channel.
Topic 5.2 Channel-forming equipment with frequency division of channels.
Technical data TT – 144
The TT-144 equipment is used to organize low-speed channels on the backbone sections of the telegraph network and data transmission network. The TT-144 voice-frequency telegraphy equipment allows organizing up to 144 two-way discrete channels in the frequency band of the TC channel of cable, overhead and radio relay communication lines. The equipment uses frequency division and frequency modulation. In one HF channel, the equipment allows you to organize the following number of discrete channels: 24 with a speed of 50 Baud, or 12 with a speed of 100 Baud, or 6 with a speed of 200 Baud, or 1 with a speed of 1200 Baud and 6 with a speed of 50 Baud (or 2 with a speed of 200 Baud). The numbering of channels, carrier frequencies, the distance between them and the frequency deviation" in the linear spectrum of the PM channel comply with the requirements of GOST and the recommendations of the CCITT. The equipment also makes it possible to organize mixed different-speed groups of channels in the PM channel.
The equipment uses the principle of individual-group conversion. The group of channels occupying the frequency band 3.6...5.01 kHz was taken as the initial one. For conversion, group carriers with frequencies of 5.4 and 6.84 kHz are used. The equipment can be connected to telegraph devices, equipment and subscriber data transmission kits, switching telegraph stations operating in bipolar bursts with a voltage of ±(5 ... 25) V. In TT channels under normal operating conditions, edge distortions do not exceed 5%. The input and output impedances of the CT channels are 1000 Ohms.
Block diagram of TT-144 equipment
The block diagram of the TT-144 equipment contains the main blocks: RNG frequency grid generator blocks, interface blocks C, linear equipment blocks LO, channel blocks K, dominance compensator block KP, power supplies. In addition, there are a number of auxiliary blocks.
The frequency grid generator is designed to generate the entire set of highly stable frequencies necessary for the functioning of equipment components. It consists of a block of reference frequency frequencies. block of group frequencies HF. blocks of linear frequencies LC, blocks of shapers F. The block OC contains a quartz oscillator and provides the formation of periodic pulse oscillations with a frequency of 3,932,160 Hz for the operation of the remaining RNG blocks. To generate 21 linear frequencies, there are seven identical blocks LC1-LC7. To change the linear frequencies of the channels, the LF outputs are connected to the channel blocks through the LF linear frequency switching board. The HF block is designed to generate oscillations of carrier frequencies (5.40 and 6.84 kHz) of group converters and a frequency of 2.7 kHz to control the CFP. Frequency modulators and demodulators of blocks K are provided with the necessary frequencies using two blocks F, each containing five shapers that perform the functions of power amplifiers.
The LO block is designed to coordinate the PM channel with individual equipment of TT channels in terms of frequency spectrum, levels and resistance, as well as to signal an understatement of the level in the PM channel. It consists of transmitting and receiving parts, each of which has two signal conversion paths, with a conversion frequency of 5.4 kHz (group A) and 6.84 Hz (group B). The block contains group spectrum converters P, amplifiers Ус and low-pass filters. In group low-pass filters, transmissions are delayed from entering the PM channel by harmonic components from the carrier frequencies and upper sidebands present at the outputs of the phase filter. In the group low-pass filters of the receiving part, the spectrum of the group signal is limited to eliminate the influence of the multiband PPC.
In the group amplifier of the receiving part of the LO block, a stepped AGC is used. When the group signal level is reduced by 9 dB, the gain of the group amplifier increases stepwise by 9 dB. The interface device C is individual equipment designed to convert signals coming from local telegraph circuits (voltage and current) into the signals necessary for the operation of the K channel unit (at transmission), and the reverse conversion (at reception). One block C houses three interface devices, each of which consists of an input and output device. Interface devices are universal and are used for all information transmission rates provided in the equipment.
In the universal block K, DC telegraph messages are converted into frequency-modulated signals in transmission and frequency-modulated signals into telegraph messages in reception. The block consists of a transmitter and a receiver, and all its nodes are located on two boards: on one KFP per and KFP pr, and on the other the remaining devices. Block K, using soldering, can be switched to one of three modes to operate at a nominal speed of 50, 100 and 200 baud/Frequency modulators and frequency detectors of the block operate in all modes at an average frequency of 2.7 kHz.
The transmitter of the universal channel block consists of the following main components: an FM frequency modulator, an additional transmission filter (not shown in the figure) and a switched transmission filter-converter KFP AC. The FM inputs from the RNG receive pulse sequences that are multiples of the lower characteristic frequency and the difference in characteristic frequencies. Depending on the polarity of the messages coming from the interface device, a lower or upper characteristic frequency is generated at the FM output. In the absence of a telegraph signal at the input of the equipment, the lower characteristic frequency is sent to the FM output.
The additional transmitter filter is a low-pass filter and is designed to retain the odd harmonics of the square wave signal coming from the FM output. The switched filter of the transmit converter is used to retain the spectral components of the FM signal located outside the frequency band allocated to the channel, as well as to move the spectrum of the channel signal CT from an average frequency of 2.7 kHz to a linear frequency of 3.66-.-4.98 kHz, specific for each channel. To do this, a control signal fl is supplied to one of the inputs of the CFP per from the RNG With frequency equal to the required linear frequency of the channel in the group.
Drawing. Block diagram of TT-144
The receiver of the channel block consists of a CFP pr., an additional reception filter DF pr. amplifier-limiter (CA), and a frequency discriminator BH. LPF. PU threshold device, as well as remote control level detector circuits (DF pr. and remote control are not shown in Fig. 8.34). From the group signal, the CFP pr. selects oscillations of a given CT channel and transfers the spectrum of the selected signal from the linear frequency to the frequency of 2.7 kHz. An additional reception filter delays the odd signal harmonics generated at the output of the CFP, etc. The limiting amplifier used in the equipment is described in detail in § 8.2.1. The frequency discriminator converts the FM signal into a series of pulses, the duration of which depends on the frequency of the input signal; the principle of its operation is similar to the operation of the TT-12 black hole equipment.
The low-pass filter selects a constant component from the pulse sequence at the output of the black hole, the value of which changes linearly as the frequency at the receiver input changes. The channel threshold device is designed to generate rectangular telegraph signals. Bipolar rectangular pulses generated by the PU control the operation of the output device of block C. When the signal level at the receiver input is below the minimum permissible value, the remote control generates a blocking signal that sets the PU to a position that ensures the appearance of a starting message in the local telegraph circuit. From the CP predominance compensator block, the PU also receives a dominance compensation signal generated by the CP when the frequency shifts in the PM channel. The CP block contains a transmitter that produces an unmodulated signal with a frequency of 3.3 kHz, and a receiver similar to the receiver of the TT channel. except that after the black hole the signal is sent not to the control unit, but to the inverting amplifier. At the output of the receiver of this channel, a constant voltage is generated, the value of which is proportional to the frequency shift in the PM channel. This voltage is supplied to the threshold devices of CT receivers of all channels and changes their response thresholds, thus eliminating dominance distortions.
The 1200 baud BC channel block, which is part of the TT-144 equipment and provides, using frequency modulation, the transmission of discrete signals at speeds of up to 1200 baud, differs from other blocks in that it contains an individual quartz oscillator and non-QFPs are used as bandpass filters , and 2,C-filters. Compared to the TT-48 and TT-12 equipment, the TT-144 equipment has expanded the composition of operational devices, which allows reducing the time spent on equipment maintenance. These devices include a test signal sensor DS, a control unit for the voice-frequency channel KCH, an indication unit BI with an intercom, and signaling units BS1 and BS2. The BS2 alarm unit is included in each TT-48 section, all other units are located in the RKS control and alarm row. In the DS, test telegraph signals of the type 1: 1 are generated with speeds of 50, 100, 200 and 1200 Baud, as well as the signals “Pressing +” and “Pressing -”. With the help of BI, operational monitoring is carried out: currents and voltages in local circuits; levels at linear inputs and outputs, as well as at the inputs of the control device; presence of predominance (up to ±10%) at channel outputs. The display unit also allows you to organize telephone conversations during measurements and when the equipment enters into communication. The KFC block is designed to control in the TC channel a decrease in the signal-to-interference ratio (with response limits of 18, 24 and 30 dB) and a shift in the control frequency exceeding the set threshold value of 2, 4, 6, 8 or 10 Hz. Blocks BS1 and BS2 generate signals for turning on emergency and warning alarms. The alarm is triggered when the RNG, power supply units are faulty, fuses are blown, the reception level of any TT channel is underestimated by 18 dB or the reception level in the TC channel is more than 20 dB. A warning alarm is triggered when the overall reception level in the PM channel is lowered by more than 9 dB, the established threshold for monitoring the signal-to-interference ratio is exceeded, or the frequency drift in the telephone channel is exceeded.
Questions for self-control
1. List the technical characteristics of the TT-144.
2. Explain the composition and purpose of the channel transmitter.
3. Explain the composition and purpose of the channel receiver.
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Equipment for urban telegraph communications TVU-15 is installed in urban and suburban sections of the telegraph network instead of equipment TVU 12M. It is distinguished by a more advanced element base, higher reliability, a developed system of service equipment that allows reducing labor costs for maintenance and repair, and improved quality characteristics of the linear path I discrete channels, significantly better energy and mass-dimensional indicators.
TVU-15 equipment, using the time division method, provides the organization of 15 telegraph channels and low-speed data transmission channels with a transmission speed of up to 200 Baud. At the interstation section, two two-wire physical circuits of GTS cables are used to transmit the group signal. In the PBX-subscriber section, discrete signals are transmitted either over a line used simultaneously for telephone communication (if the attenuation of the physical circuit is less than 6 dB at a frequency of 800 Hz), or through a dedicated two-wire physical circuit with a loop resistance of 4 kOhm. TVU-15 has the ability to change the group transmission rate and combine channels, which allows you to flexibly change the communication range and reduce distortions introduced by discrete channels.
Equipment composition. The TVU-15 equipment includes two terminal stations TVU-15A and TVU-15B, as well as a group regenerator station TVU-15R.
The terminal station TVU-15AN, made in a desktop version (in a casing), provides the organization of 15 telegraph channels and is installed at the telegraph office or terminal point. The parameters of telegraph circuits are determined by GOST 22937-78.
The terminal station TVU-15BN, made in a desktop version, ensures the concentration of telegraph communications on the PBX by connecting 15 subscriber physical cable circuits through subscriber devices and is installed on the PBX.
The TVU-15R-N station, made in a desktop version, contains two double-sided regenerators and is installed in a telephone exchange.
Stations TVU-15AS, TVU-15BS, TVU-15RS, made in rack design, are intended for installation on the TVU-15SU rack. The purpose of the stations is similar to the corresponding desktop stations. The TVU-15AS station houses two semi-sets of TVU-15A stations operating in two communication directions.
The TVU-15SU universal rack allows you to place up to six stations of the TVU-15AS, TVU-16RS, TVU-15BS types and is installed on a telegraph office or automatic telephone exchange. If necessary, desktop stations TVU-15AN and TVU-15RN with removed casings can also be installed on the TVU-15SU rack.
TVU-15B stations include 15 subscriber devices, consisting of station and subscriber semi-sets.
Transfer of information from the regional telephone exchange where the end station is installed
TVU-15B, to the final installations the following is carried out:
For terminal installations connected to channels 1-12 of equipment equipped with subscriber separating duplex devices (URDK), - via cable subscriber telephone lines, the attenuation of which at a frequency of 800 Hz is no more than 6.0 dB. The devices provide two-way simultaneous exchange of discrete information at speeds up to 200 Baud; At the same time, telephone communication is maintained;
For remote terminal installations connected to channels 13-15 of equipment equipped with subscriber half-duplex devices (UPDL), - via dedicated physical circuits of GTS cables, the loop resistance of which does not exceed 4 Ohms. The devices provide two-way sequential information exchange at speeds up to 100 Baud. The URDC-S and UPDL-S devices are structurally interchangeable.
The terminal station TVU-15AN contains:
Individual muldex equipment, consisting of five blocks of interface devices (US) with 3 channels each;
Group muldex equipment, consisting of “transmitter, receiver, cyclic phasing and control blocks, master oscillator, signal conversion device;
Power supply devices: one rectifier (RV) and power supply unit PSU;
Auxiliary devices, including an indication unit (BI), a station loop switching device (UVSh-S), a service communication and alarm device (UAS).
The TVU-15AS end stations include two sets of individual and group muldex equipment, as well as a power supply unit (PSU). The remaining blocks are located on the control and auxiliary device unit (CAD) of the rack and are common to all stations installed on the rack.
The TVU-15B end stations include: individual subscriber devices (station and subscriber semi-sets) URDC in the amount of 12 pcs. and UPDL in the amount of 3 pcs.; muldex group equipment, power supply. In a desktop station, the display unit and the separating filter unit (BRF) are located in the station, and in rack-mount stations BI - on the KVU block of the rack, and the filters - on the BRF block.
The TVU-15R intermediate station includes two sets of double-sided regenerators and a power supply. In a table-top station, the display unit is located on the station, and in a rack-mount station - on the KVU block of the rack. “Each two-way regenerator TVU-15R contains two signal conversion devices, two GZI generators and one UVSh-R loop switching device.
The TVU-15SU rack includes: block of input-output devices;
Separating filter block (equipped with filter cells for TVU-15B stations when installing a rack on a telephone exchange);
A block of control and auxiliary devices KVU, containing: three rectifiers powering two rack units each, an indication unit, a station loop switching device, an official communication and alarm device, a power supply.
^ Technical data. Transmission of telegraph signals in an individual channel is carried out by the superposition method.
The type of sealed connecting communication lines is two two-wire physical circuits of GTS cable lines of any type, except those that are powered and equipped with bridge amplifiers.
The transmission of a group signal to the communication line is carried out using a bipulse signal with the following algorithm: “ones” of a group binary signal are transmitted by pulses of alternating polarity with a duration equal to the frequency period of the group signal, “zeros” are transmitted by a bipulse consisting of two antiphase pulses with a fixed polarity and duration each equal to the half-cycle of the clock frequency of the group signal. Linear signal pulse amplitude ±3.3 V ±10%. The group signal transmission rate can be set to 64, 32 and 16 kBaud. The maximum pulse repetition rate in the communication line is correspondingly equal to
64, 32, 16 kHz.
Internal input and output resistance of the equipment from the communication line side
Less than 150 ohms.
The maximum number of code-independent telegraph channels is 15. The nominal transmission speed in channels is up to 200 Baud.
The degree of start-stop distortion introduced by the equipment channels at a group signal transmission rate of 64 kBaud: at a speed of 50 Baud - no more than 3%; at a speed of 100 Baud - no more than 5%; at a speed of 200 Baud - no more than 6%. As the group transmission rate decreases, the amount of introduced distortion increases proportionally. The amount of distortion introduced by the equipment channels can be reduced by combining channels in twos or four (1- and 2-, 3- and 4-, 5- and 6-, 7- and 8-, 1-, 2-, 5- and 6th; 3-, 4-, 7th and 8th channels). The maximum attenuation of a physical two-wire circuit between any two equipment stations is 43 dB at the maximum frequency equal to the group signal transmission rate (64 , 32 or 16 kHz). The maximum number of regenerators in a linear path is five.
The parameters of the URDC devices are similar to the parameters of the URAL TVU-12M devices. The parameters of UPDL devices are similar to the parameters of PU devices.
The parameters of local telegraph circuits of the TVU-15A station and subscriber devices URDC-A and UPDL-A comply with GOST 22937-78.
The TVU-15BN, TVU-15RN stations are powered from a station battery with a voltage of 60 V±10% (with the “plus” circuit grounded).
The power supply of subscriber devices URDC-A and UPDL-A is carried out from an alternating current network with a frequency of 50 Hz and a rated voltage of 127 or 220 V with fluctuations from 108 to 140 V or from 187 to 242 V, respectively.
The TVU-15N station and the TVU-15SU rack are powered from the main source - an alternating current network with the parameters indicated above. In the event of a power failure from the main source, power is supplied from a backup source - a 60 ± 6 V station battery. The transition to power from the backup source and return to power from the main source is carried out automatically.
Power consumption: from the alternating current network for TVU-15AN and TVU-15SU (without stations) no more than 40 and 50 VA; from the DC network - no more than 25 W for all types of stations.
Overall dimensions: desktop stations 250 X 550 X 282 mm; rack-mount stations 240 X 550 X 212 mm; racks TVU-15SU 2600 X 600 X 250 mm; subscriber devices 335 X 205 X 72 mm.
Weight of stations, no more: TVU-15AN - 18 kg, TVU-15AS-13 kg, TVU-15BN - 17 kg, TVU-15BS-14 kg, TVU-15RN - 15 kg, TVU-15RS-11 kg, racks TVU- 15SU -95 kg.
^ Operating principle. The principles of construction and operation of TVU-15 equipment are similar to the principles of construction and operation of TVU-12M equipment, although the technical implementation of these principles is different. The main differences between TVU-15 and TVU-12M are as follows:
The number of telegraph channels has been increased to 15, the 16th channel is used for synchronization;
The maximum number of regenerators in a linear path has been increased to five (instead of two);
It is possible to reduce the group speed from 64 to 32 or 16 kBaud, which allows, if necessary, to increase the length of the regeneration section by 2 or 4 km, respectively (for cable TG-0.5);
It is possible to combine channels of two and four, which allows, if necessary, to reduce the amount of introduced distortion;
Bipulse coding in the linear path and quartz frequency stabilization of the master oscillators were used, which made it possible to increase the noise immunity of the signal, eliminate the need for careful correction of the line frequency response and greatly simplify the process of setting up equipment when connected to the line;
A developed system for monitoring the functioning of equipment from cells to equipment as a whole has been introduced;
The possibility of remote organization from the main station of loops along the linear circuits of any of the intermediate stations has been introduced to determine the faulty section;
Service acoustic communication between stations via a phantom circuit has been introduced; current monitoring of the error rate of the received linear signal has been introduced;
A control channel has been introduced, covering with continuous monitoring the path from the main station through intermediate stations and connected by a loop at the second terminal station. The result of automatic control is displayed at the main station;
^ Hardware DATE
DATA equipment (duplex subscriber telegraph equipment) is designed to organize bundles of channels to city branches or end points included in the network of direct connections of the substation, subscriber telegraph AT or the PD data transmission network. It provides the organization of two-way telegraph communication at speeds of up to 100 and 200 baud over two-wire physical circuits of the city telephone network. At the same time, the standards for the influence of telegraph transmission on neighboring telephone circuits and wired broadcast channels, the required transmission quality, and the standards for the stability of the parameters of telegraph channels and their independence from the line parameters are met.
The telegraphing range at a transmission level of 0 dB is determined by the overlapped attenuation of 30 dB and is equal to 20 km when using DATA-3 channel equipment and cable
TG-0.5 and 35 km when using cable TZ-0.9. Six-channel DATA-6 equipment via the same cables provides telegraphing ranges of up to 15 and 28 km, respectively.
The DATA equipment consists of two semi-sets: the terminal DATA-PO and the station DATA-BS. A control and measurement unit is also installed on the station semi-set, with the help of which the entire range of operational checks is carried out.
Two modifications of DATA equipment are produced: three-channel DATA-3 and six-channel DATA-6. DATA-3 equipment allows you to organize three communication channels at a speed of 100 Baud or one channel at a speed of 100 Baud and one at a speed of 200 Baud. The DATA-6 equipment allows you to simultaneously organize five channels at a speed of 100 Baud and one at a speed of 200 Baud.
The station half-set DATA-3-BS provides operation with three terminal half-sets DATA-3-PO. The six-channel version of the DATA-6-BS station semi-set provides operation with only two DATA-6-PO semi-sets. As a result, the group transmission rate is 2400 bps when using DATA-3 equipment and 4800 bps when using DATA-6 equipment.
The equipment uses a pulse-code transmission method with time division of channels. In this case, simultaneous two-way telegraphy is ensured thanks to the bridge (balanced) method of separating transmission and reception. The bridge method of separating transmission directions requires at least 2 times narrower frequency bandwidth compared to frequency or time.
Figure 23 - Block diagram of DATE equipment
The block diagram of the DATA equipment is shown in Fig. 23. Telegraph signals with voltage from ±5 to ±25 V from the output of the calling device, ISU-TA or subscriber panel of switching station AP KS arrive at the input device VU and the encoder (coding device) of the DATE equipment. The encoder converts bipolar telegraph signals into a pulse code signal. The latter, as well as a 1:1 signal from the synchronization sensor DSK supplied to the transmission distributor R a.n. which is triggered by clock pulses of the master generator oscillator. The frequency of the clock pulses determines the time separation of the channels. The group multichannel signal from the Rper output is supplied to the linear cell transmitter.
The transmitter is an electronic relay that converts a single-pole group signal into a two-pole one. Output signal Per is fed to one of the diagonals of the bridge circuit for decoupling reception and transmission. The arms of the bridge are composed of a variable-resistance resistor of the balanced circuit Z b, a resistor equivalent to the line resistance, and two resistors of equal resistance. The bridge is balanced using Z b. With the correct balance setting, the transmitter signal practically does not arrive at the input of the receiver of its station, since the attenuation between the transmitter and the receiver is at least 43 dB. This method of separating transmission directions allows for counter transmission in the same frequency band, and therefore, the use of the same equipment at both ends of the communication line.
The receiver converts the bipolar signal voltage ± (5-20) V into a single-pole asymmetrical group signal, which is then fed to the reception distributor R PR and the phase-locked loop circuit PLL. Scheme PLL ensures the isolation of oscillations in the clock frequency of the transmitter of the opposite station and the synchronization of R PR and R AC. The Rpr distributor produces a clock signal that enters the phasing unit in cycles BFC, phasing R pr and R lane. As a result, the signal of the individual channel is separated from the group signal in the receiving distributor. The sequence of pulses corresponding to the selected individual channel is fed to the receiving part of the codec - the decoder. Using decoder and electronic relay output ER The telegraph signal is regenerated and then fed to the telegraph receiver TA. As a result of regeneration, signal distortion at a speed of 50 Baud does not exceed 4%, and at speeds of 100 and 200 Baud - 7%.
^ Topic 16. Channel-forming equipment with PDK: TT – 144, TT-24.
Channel-forming equipment TT-144 is designed for secondary sealing of standard 4-wire channels of PM cable, overhead, radio relay or satellite communication lines.
Compaction is carried out using the frequency division method using frequency modulation. The equipment is designed to organize TT channels at speeds of 50, 100, 200 AND 1200 Baud.
Six TC channels can be connected to one equipment rack, each of which can accommodate 24 50-baud TT channels, or 12 100-baud channels, or six 200-baud channels. When transmitting at 1200 baud, one TC channel can accommodate only one 1200 baud TT channel plus six 50 baud channels. It is possible to organize mixed systems by replacing channel blocks.
The TT-144 equipment uses one universal channel block, in which to switch from one telegraph speed to another it is enough to make several solder connections.
The TT-144 equipment compares favorably with previous versions (including the TT-12), since it eliminates the need to have units at different speeds in stock, therefore, redundancy and repair are simplified.
The equipment has automatic compensation for the frequency shift of the received signal, which practically eliminated the increase in edge distortion due to the instability of the PM channel. As a result, the only reason for the appearance of edge distortions remained the temperature instability of the amplitude-frequency characteristics of bandpass filters. The influence of this reason in the TT-144 equipment is reduced by using active switched C-filters - converters (CFCs) instead of LC filters. The average frequency of the CFP passband is also stabilized by quartz. As a result, the instability of the characteristics when telegraphing at a speed of 50 Baud is only 0.25 Hz when the ambient temperature changes by 30 ° C and does not depend on the value of the average frequency of the filter passband.
Thanks to a set of stabilization measures, the permissible degree of edge distortion for the CT channel under nominal operating conditions at speeds of 50, 100 and 200 Baud is 5%, and at a speed of 1200 Baud - 10%.
In parallel with the increase in the number of TT channels in the TT-144 equipment, the power consumption from the power supply unit has been significantly reduced. This, on the one hand, made it possible not to install a more powerful power supply system at the communication center, and on the other hand, it made it possible to alleviate the thermal conditions of the equipment itself.
This advantage was achieved thanks to the optimal choice of microcircuits that provide digital signal processing. Analog circuits are built on K153UD2 operational amplifiers. As a result of this, as well as a number of other measures, the power consumption of the equipment per channel is reduced to 3 V∙A compared to 11 V∙A in the TT-12.
The TT-144 equipment introduced control of residual attenuation, frequency shift and signal-to-interference ratio in the PM channel; built-in monitoring equipment allows you to monitor the signal voltage at the input and output of channels, supply voltage, the magnitude of predominance at the output of channels up to 10%, the overall level at linear inputs and outputs, and the levels at the input of limiting amplifiers. Emergency and warning alarms are provided. The first has an output to a station-wide alarm and is triggered when there is a malfunction of the frequency grid generator blocks, power supplies, loss of supply voltage, as well as when the level at the input of any TT channel block and the general level in the TC channel decreases by 20 dB relative to the nominal one. All this allows you to reduce the time for operational maintenance of TT equipment.
The optical warning alarm also has a station-wide output and is triggered when the general reception level in the PM channel decreases by 9 dB against the established norm, as well as when the frequency shifts and the signal-to-interference ratio deteriorates.
For frequency shift signaling, a variable response threshold is provided, which can be set from 2 to 10 Hz in steps of 2 Hz. The threshold for triggering a signal about reducing the signal-to-interference ratio can also be changed in steps of 6 dB in the range from 18 to 30 dB.
Figure 24 shows a simplified block diagram of the TT-144 equipment. It consists of three main parts: an individual transformation path, a group transformation path and a stabilization system. Thus, the TT-144 equipment uses the principle of individual-group conversion. The individual conversion path includes a BS interface block and a BC channel block.
The group conversion path includes elements of the linear equipment block ^ BLO.
The stabilization system is a frequency grid generator RNG, which, from the oscillations of a highly stable reference frequency generator, forms 2.7 kHz oscillations that control switched filter-converters (KFP), stabilizing the frequency-modulated FM generator and the frequency discriminator of the BH, as well as a grid of carrier frequencies for the CFP in the range of 3.66-4.98 kHz and linear conversion frequencies of 5.4 and 6.84 kHz.
Figure 24 - Block diagram of the TT-144 equipment.
Figure 25 shows the signal conversion diagram. Signals from all transmitting telegraph devices or Gper data transmission equipment (Fig. 1) are divided into two groups: A and B. In both groups, therefore, there are 12 telegraph signals. All of them are fed through the input device Uykh. The input device Uvkh converts the level of a bipolar signal in local circuits to the level necessary for the operation of FM equipment. Telegraph messages control the operation of the transmitter, which, depending on the polarity of the input telegraph message, produces one of the characteristic frequencies relative to the average frequency of 2.7 kHz. The latter is the same for all BCs and for all speeds.
Figure 25 - Frequency conversion in TT equipment - 144
As a result of transformation using KFP spectrum of the signal of each channel in FM, it is transferred to the band 3.6-5.04 kHz. The position of the signal spectrum of each channel in this band depends on the individual carrier frequency / n, matched to the telegraphy speed.
For telegraph speed 50 baud s ^ RNG via carrier frequency switch ELF for each of twelve BC carrier oscillations are supplied in the range of 3.66-4.98 kHz with an interval of 0.12 kHz. For 100 baud, the carrier frequency range is 3.72-4.92 kHz with an interval of 0.24 kHz; for a speed of 200 Baud, the carrier range is 3.84-4.8 kHz with an interval of 0.48 kHz. For a 1200 baud channel, an 1800 Hz carrier is used with characteristic frequency spacing
Formed groups of 12 signals are fed to group converters ^P(Fig. 1) linear equipment unit BLO. Here they are carried using group carriers 5.4 and 6.84 kHz: group A to the lower part of the PM band (0.36-1.8 kHz), and the group B- in the upper (1.8--3.3 kHz).
Generated group spectrum through an amplifier ^ Us and low pass filter LPF is fed into the PM channel.
The incoming group signal is converted in reverse order in the receiving paths BLO And BK. and in the form of a bipolar signal is supplied to the receiver TPR.
To eliminate predominance as a result of frequency shifts in the PM channel, the TT-144 equipment includes an automatic predominance compensator KP. It contains a transmitter that generates an unmodulated signal of a control frequency of 3.3 kHz, and a receiver.
At the output of the latter, in the presence of a frequency shift in the PM channel, a constant voltage is formed, the sign of which is consistent with the sign of the shift, and the value is proportional to the frequency shift within ±10 Hz.
A constant voltage is applied to the threshold device of the receiver of each CT channel and its response threshold is changed accordingly, thus eliminating the dominance.
^ INTRA-REGIONAL (ZONE) VOLTON TELEGRAPHY EQUIPMENT TT-24
Frequency modulation equipment TT-24 is designed for organizing intra-regional telegraph communications and operates via PM channels of cable, overhead or radio relay lines.
The TT-24 equipment (overall dimensions 520 X 600 X 225 mm) allows you to organize up to 24 duplex telegraph connections and provides connection to up to four TC channels. Four sets of equipment can be mounted on a 2600 mm high cabinet
The equipment makes it possible to organize in one PM channel: 24 channels with a nominal transmission rate of 50 Baud; 12 channels with a transmission rate of 100 Baud; six channels with a transmission rate of 200 baud; 1 channel with a transmission rate of 1200 Baud plus six channels with a transmission rate of 50 Baud, two channels with a transmission rate of 200 Baud, or three channels with a transmission rate of 50 Baud and one 200 Baud (the 1200 Baud channel occupies the middle, part of the spectrum of the PM channel).
It is possible to organize both homogeneous TT systems with the same type of channels, and mixed ones with channels of different types.
Since all the units in the TT-24 equipment are unified with the corresponding units of the TT-144 equipment and have the same electrical parameters with them, the TT-24 equipment has all the advantages of the TT-144 equipment (increased operating stability, low power consumption, the ability to control basic parameters channel TC).
The equipment uses a universal channel block with transmission speeds of 50, 100 and 200 baud, which allows you to change the speed of operation in TT channels and the composition of TT systems under operating conditions without purchasing new blocks.
The TT-24 equipment consists of TT-24 sections, a series of control and alarm systems, and a linear panel. Section TT-24 contains a complete set of equipment for organizing 24 TT channels and can be installed on a table or hung on a cabinet. The control and alarm series differs from the similar series of TT-144 equipment only in the presence of legs for installing it on the TT-24 section or on a table.
The TT-24 equipment can work together with the TT-144, TT-12, TT-48 equipment installed at the opposite station, however, joint work with the TT-48 equipment is allowed only in exceptional cases.
Maintenance of the equipment is one-sided, weight no more than 70 kg.
The equipment is powered in one of three modes:
A) from a DC network with a voltage of 60 V±10%;
B) from a single-phase alternating current network with a voltage of 220 V (5% and part 50±2 Hz;
B) from a single-phase AC network with a voltage of 220 V, 1 "%, frequency 50±2 Hz and automatic switching to a backup DC source with a voltage of -60 V when the AC network drops below 187 V. When switching the power, interruptions in linear telegraph circuits are missing.
In operating mode, the equipment consumes no more than 115 VA from the AC mains, and no more than 70 W from the DC source.
The emergency and warning alarm system of the TT-24 equipment is similar to the alarm system of the TT-144 equipment.
The signaling circuits are designed to be powered from an external source -60 or -24 V; the maximum possible current consumption does not exceed 600 mA,
The following four Modifications of TT-24 are supplied;
A) section TT-24! containing a number of control and alarm systems, an input panel. Sections Equipped with a 24-channel 50-baud TT system;
B) section TT-24, which differs from the previous modification in the composition of the TT system. The section is equipped with a 20-channel CT system, containing one channel for 100 and 200 Baud, 18 channels for 50 Baud and four reserve channels;
B) section TT-24, equipped with a 24-channel 50-baud TT system;
D) section TT-24, equipped with a 20-channel TT system with four backup channels.
The last two modifications are intended for installation on a cabinet together with one of the first two modifications.
The following are supplied under a separate agreement:
A) a cabinet designed to install four 24-channel sections and a number of control and alarm sections;
B) channel block 1200 Baud. On each TT-24 section, one channel block for 1200 Baud can be installed instead of two channel blocks for 50, 100, 200 Baud.
