TT 48 gums technical description. Automatic telephone exchange
This equipment is designed to obtain large channel bundles, which can primarily be achieved by increasing the specific information transmission rate (bit/Hz).
For many years, the KOA of trunk connections was built mainly on the use of CRC and FM. From 1963 to 1973 TG-17P equipment was produced, which provided the organization of 17 “transparent” telegraph channels through which it was possible to transmit at speeds up to 75 baud. Since 1972, serial production of TT-48 equipment (Desna) has been launched. Currently, this equipment is widely used in trunk communications. With its help, in one PM channel you can organize 24, 12 and 6 channels with a telegraph speed of 50, 100 and 200 Baud, respectively. The channels are transparent. All equipment parameters comply with CCITT requirements.
The principle of constructing the equipment is individual, i.e., each telegraph channel occupies the corresponding section of the PM without additional group conversion. Compared to the TT-17P, the equipment has better operational and technical characteristics per channel; it occupies 3 times less area, is more than 2 times lighter and consumes 1.5 times less electricity.
Further improvement of traditional TT systems with FM follows the path of improving operational and technical characteristics and quality indicators. The TT-144 equipment also complies with the CCITT Recommendations and has the same basic technical data as the TT-48 equipment. Due to the widespread use of microcircuits, the developed equipment makes it possible to place not 48 channels (like TT-48), but 144 channels on one standard building. The equipment provides for the organization of channels up to 1200 Baud. The equipment is more reliable in operation, requires less time for maintenance, and is more convenient to operate. Compared to the TT-48, power consumption is reduced by more than 3 times, and the weight per channel is significantly reduced.
Along with the improvement of traditional TT systems with VRK, a KOA with VRK is being created.
Since 1980, the USSR telegraph network began introducing DUMKA equipment (duplex channel-forming equipment), which allows: in comparison with TT-48 and TT-144, to increase the efficiency of using the frequency band of the TC channel by 2-2.5 times; reduce the signal power at the equipment output; reduce the cost of the communication channel by 1.5-3 times. The equipment allows you to organize 23 “transparent” and 45 “opaque” channels at a speed of 50 baud. In code-dependent channels, the transmission of start-stop signals must be carried out using the MTK-2 code with a 7.5-pin division. By combining two and four code-independent channels with a nominal transmission rate of 50 baud, a code-independent channel can be obtained for transmission at speeds of 100 and 200 baud, respectively.
The DUMKA equipment uses the time principle of channel formation and the method of generating SIP signals, discussed in Chapter. 5.
The block diagram of the DUMKA equipment (Fig. 6.81) contains an MP tipplexer, an RCD and a UPS.
Rice. 6.81. Block diagram of DUMKA equipment
Each block has a transmitting and receiving part. The combination of discrete signals into a group signal is carried out in MP transmission. The group signal of the GS is fed to the RCD, where it is divided into blocks, into each of which testing elements are introduced that allow errors to be corrected during reception. The signal conversion device of the transmitting part converts the signal supplied to its input using two-level amplitude and single relative phase modulation with partially suppressed one side (AM-RPM OBP). At the receiving side, the signal is amplified in the UPS and converted into a discrete group signal. In the RCD, errors are corrected, and in the reception MP, individual signals are separated and decoded, after which they can each be sent to their own telegraph apparatus.
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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
- a dominance indicator that ensures the accuracy of dominance elimination is no 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.
The PTK VECTOR-VT administration system software is a Web application that runs in any Internet browser (Internet Explorer, Opera, Mozilla Firefox). Thus, to monitor and manage the device, there is no need to install any specialized software on the administrator’s computer.
The administration system allows you to perform the following tasks:
- configuration of telegraph channels;
- configuring PM channels;
- configuration of the PM channel with multiplexing of telegraph channels and telephone channel; adding, deleting and configuring IP virtual channels;
- configuration of code-independent channels of IP-special consumers;
- carrying out measurements on telegraph channels;
- monitoring the status of any type of channels;
- adding, deleting and modifying alarm profiles;
- backup archiving and quick restoration of settings of PTC VECTOR-VT.
Configuring telegraph channels
The administration system allows you to perform all the basic actions necessary to configure telegraph channels:
- setting the data transfer rate over the channel corresponding to the operating speed of the connected subscriber (select from a list of 50, 100, 200 Baud);
- selecting an alarm type from the list of profiles. From the list you can select both a code-dependent signaling profile and a code-independent mode of operation of the special consumer channel;
- turning off a channel if it is not in use;
- setting routes for organizing connections with a TT channel or a virtual IP channel.
Configuring PM channels
Basic actions when working with PM channels:
- selecting the type of equipment from the list of preset configurations of PM channels for the corresponding types of equipment (TT-5, TT-12, TT-24, TT-48, TT-144, P-327, P-318, P-314, etc.);
- manual configuration of the distribution of TT channels in the TC channel for mixed-type systems or for those not included in the list of preset configurations;
- setting the levels of input and output signals, as well as turning on or off the transmission of the control frequency;
- Configuring the TC channel using the spectrum of the TC channel to compress telegraph channels and telephone channels comes down to selecting the appropriate type of equipment and setting the telephone filter mode. As a result, one of the PM channels will be used as a compressed telegraph and telephone channel, and the second will be used to connect a telephone line.
Configuration capabilities allow you to configure the channel to work with any type of equipment with frequency division of TT channels at an adjacent node.
Configuring IP channels
For IP channels, operations are available to create an almost unlimited number of virtual telegraph channels and various manipulations with them. The speed of the IP channel is determined automatically, eliminating the need to manually set the data transfer rate over the channel. Configuration comes down to specifying routes for organizing connections with physical telegraph lines and TT channels.
Virtual telegraph channels support data transmission in a code-independent mode for the traffic of special consumers over an IP network. This mode is activated automatically when a connection is established with a code-independent telegraph channel serving a special consumer. Thus, no additional actions are required to connect a special consumer to the IP network.
Carrying out measurements of telegraph channels
The administration system allows you to carry out measurements on physical telegraph channels and TT channels. All actions are available both for a separately selected channel and for a randomly selected group of channels.
If necessary, you can turn the telegraph channel towards adjacent equipment.
You can output a signal of positive and negative polarity into the telegraph channel, and also turn off the channel output.
Towards adjacent equipment, “point” test signals can be transmitted via a telegraph channel with a choice of speeds of 50, 100, 200 Baud.
If it is necessary to estimate the percentage of edge distortions in a channel, the VECTOR-VT software package has a mode for measuring “point” test signals. In this case, the speed of the measured signals and the percentage of edge distortion are displayed separately for positive and negative polarity.
Channel monitoring
The administration system allows you to remotely view the status of channels in a pool of telegraph channels, PM channels and IP pools.
The displayed information shows the real state of the working channel - the channel can be in the initial state, in operation, in testing mode, or in an emergency state. In the latter case, the cause of the accident and its duration are displayed in the administration system. This could be a break in the receiver line, a short circuit in the transmitter, polarity reversal, etc. Each channel state has a corresponding color indication.
Emergency channel conditions are accompanied, among other things, by an audible alarm on the administrator’s computer.
Manage alarm profiles
The profile settings dialog is used to manage alarms. Operations are available to create new alarm profiles, delete unused ones, as well as fine-tune existing profiles.
In most cases, pre-installed profiles with ready-made alarm settings are sufficient, but if necessary, fine adjustment allows you to connect any subscriber device with a non-standard interaction protocol to the VECTOR-VT PTC.
Backup archiving and quick restoration of settings
The administration system allows you to manage the general settings of the complex and backup the entire configuration of the VECTOR-VT software.
Saving and restoring the full configuration of the complex is carried out by the administrator’s command with “one click of the mouse”. The simplicity of this operation allows you to always have a backup copy of the configuration on your personal computer and, if necessary, in a matter of seconds, remotely restore the functionality of the VECTOR-VT software.
If a large number of devices are used in the IP network, backup of all VECTOR-VT control systems can be carried out from one personal computer connected to the IP network. At the same time, the principle of centralized management, backup and control of all devices in a distributed IP network is achieved. It is clear that, being, for example, in St. Petersburg, you can completely easily administer the VECTOR-VT software systems installed in Khabarovsk or Murmansk, if, of course, you have the appropriate access rights and are on the same IP network with them.
Alarm system
The alarm system is integrated into the administration system and is designed to notify operational and technical personnel about failures of equipment and software of the VECTOR-VT PTK, as well as about emergency situations occurring on communication lines and channels.
Alarms issued in case of failures are accompanied by audible and visual indications. In this case, there is no need to install special software; the alarm system is automatically activated when connected to the VECTOR-VT control system from a web browser from any personal computer.
Initial data
1. The designed communication house is a separate building located on a two-cable trunk communication line, and is a serviced amplification point (UPP).
· Three-story brick building, type III, located at a large station, round-the-clock and stable power supply via two lines from two points of a large power system.
· The rated alternating current voltage at the inputs of the electronic control unit of the communication house is –380 V, its fluctuations are in the range of 323-418 V. Deviations in the alternating current frequency do not exceed ±4%.
2. The LAZ of the communication house houses serviced transit amplification stations and channel-forming equipment for the end points of high-frequency (HF) transmission systems K-60p, equipment for sealing overhead and cable lines in adjacent directions, as well as operational-technological communication equipment.
· In addition, the communication house houses local telephone exchanges, long-distance switches (MTS) and autoswitching nodes (AUK) for long-distance automatic telephone communication (DATS).
Composition and quantity of equipment in the communication house
Table No. 1
| Equipment type | Quantity of equipment | Unit |
| K-60p (intermediate station PK-60p) | System | |
| K-60p (terminal station OK-60p with DP) | System | |
| K-12+12 (terminal station OK-12+12 with DP) | System | |
| Equipment for isolation and HF transit of primary groups | ||
| STPG-K | Rack | |
| Service communications and telemechanics equipment | ||
| SSS-7 | Rack | |
| TM-OUP | Set | |
| Voice-frequency telegraphy equipment TT-12 | Set | |
| Operational-technological communication equipment | ||
| PST-4-70 | Station | |
| RSDT-2-61 | Station | |
| DRS-I-69 | Station | |
| MSS-12-6-60 | Rack | |
| Long-distance and local telephone communication equipment | ||
| ATSC-100/2000 | Number | |
| UAK DATS | Channel (DATS kit) | |
| Switch |
Additional house connection loads
Table No. 2
| Load name | Installed power, kW | Power factor cosφ | Coefficient of simultaneous switching on of load devices |
| Ventilation of the battery, DGA rooms, pumps for pumping fuel DGA (guaranteed power load) | 10,4 | 0,8 | 0,6 |
| Guaranteed lighting | 8,3 | 0,92 | 0,7 |
| Emergency lighting 24 V DC | 0,3 | 1,0 | 1,0 |
| Non-guaranteed (general) lighting | 21,8 | 0,92 | 0,7 |
| Non-warranted power electrical equipment (household consumers) | 47,6 | 0,8 | 0,66 |
I. Brief characteristics of communication equipment and general requirements for electrical installations.
Each type of communication equipment has a specific purpose and has specific features that determine different requirements for power supply devices. Therefore, we will give a brief description of the equipment.
K-60p system serves to organize 60 telephone channels over symmetrical non-pupinized two-cable communication lines; Secondary multiplexing of telephone channels by voice-frequency telegraph and photo telegraph, transmission of signals from data transmission systems and long-distance radio broadcasting is possible.
Table No. 3
Terminal stations OK-60p consist of group path equipment, individual conversion and auxiliary equipment.
The equipment of the group path consists of linear amplifiers and correctors SLUK-OP, generator equipment SUGO-1-5, control frequencies SKCh and group conversion SGP
Individual conversion equipment consists of racks of individual SIP-69 and tone call converters and STV-DS-60 differential systems.
In addition, OK-60p includes: SVKO K-60p input and cable equipment rack, SDP K-60p remote power supply rack, UKVSS unified switching and calling equipment for office communications, telemechanics and telecontrol equipment, switching rack for STPG primary groups.
Intermediate serviced station PK-60p consists of one rack of linear amplifiers and correctors SLUK-OUP-2, which has a two-frequency flat-inclined automatic level control (AGC) or SLUK-OUP-3 with a three-frequency flat-inclined curved AGC. In addition, the composition includes: input and cable equipment - two SVKO K-60p racks, two SDP K-60l remote power racks, unified switching and calling equipment for office communication UKVSS, TM-OUP telemechanics equipment, telecontrol.
K-12+12 system designed for compaction of circuits in symmetrical cables with twelve telephone channels over a two-wire, two-way system and one service channel in the frequency range 8-124 kHz. In the direction from station B to station. And the lower group of frequencies 12.3-59.4 kHz and the service channel 8.3-11.4 kHz is transmitted, in the opposite direction - the upper group of frequencies 72.6-119.7 kHz and the service channel 120.6-123.7 kHz.
Telephone channels can be used for secondary multiplexing by voice-frequency telegraphy, phototelegraphy, data transmission and broadcasting.
Table No. 4
Terminal stations OK-12+12 are manufactured in three modifications: OK-12+12AA - a rack with two end stations A, OK-12+12BB - a rack with two end stations B, OK-12+12AB - with one end station A and one station. B.
Stations A and B are equipped with universal correcting devices for receiving paths. In addition to the main equipment, mounted on racks
equipment for high-frequency service channel and remote power transmission.
STPG-K
Equipment for high-frequency transit of primary groups in the 60-108 kHz spectrum from one transmission system to another with sharp suppression of currents from adjacent groups of telephone channels and control frequencies lying within the transmitted frequency band.
SSS-7
SSS-7 stand designed for organizing service communications on cable lines sealed by the K-60p transmission system. SSS-7 is used in OP and EUP without RCM. The equipment includes racks for terminal and intermediate amplification points.
TM-OUP
TM-OUP– a non-contact telemechanics system designed to control, from the OP and EUP, telemonitoring devices of the RF path of the NUP, as well as to monitor the operating conditions of the NUP equipment. The TM-OUP kit generates and transmits control commands to the communication line and receives signals from the line. Works via phantom circuits of the main cable.
TT-12– frequency-modulated voice-frequency telegraphy equipment designed for secondary multiplexing of standard four-wire voice-frequency channels (0.3-3.4 kHz) of cable, overhead or radio relay communication lines. Allows you to organize up to 12 duplex telegraph channels. The equipment allows you to organize mixed systems of voice-frequency telegraph channels of different types in terms of transmission speed.
PST-4-70
PST-4-70– a control station for 4 directions is intended for organizing station communication of the substation. Provides connection of the station to physical circuits via a two-wire system, to HF channels – via a 2- or 4-wire system; sending individual and broadcast calls to the line and receiving call control; lengthening the sending of a calling signal and long-term sending of any one calling frequency; receiving a call with a frequency of 160 Hz from intermediate points, turning on the calling lights on the switch when receiving a call and sending a signal to the line that a call has arrived at the station; two-way conversations (without amplification) between subscribers of intermediate points with the telephone operator and local communication subscribers; connecting the mechanic's intercom to the PS lines and the mechanic calling the telephone operator and any subscriber on each line. Made on semiconductor devices and relays.
RSDT-2-61
RSDT-2-61– the control station for train dispatch communications in 2 directions is intended to organize communication between the train dispatcher and subscribers included in the circle. Provides: connection of the station to physical circuits and HF channels; sending individual, group and circular calls to the line; lengthening the sending of a calling signal and long-term sending of any one calling frequency; acoustic control of sent calling frequencies and call reception; the ability to connect the train dispatcher's communication channel to the train radio communication channel through the control radio communication station unit BRPS-62M.
DRS-I-69
Station DRS-I-69 makes it possible to: loudspeaker reception of speech from all points of the road police station; communication with all points according to the principle “one speaks, everyone hears”. Inclusion of three four-wire channels for communication with executive stations; selective calling to 18 long-distance points and 20 local subscribers; connecting two lines of distant points using a two-wire circuit, etc.
The following blocks are installed on the DRS-I-69 rack: input, control, distributor, intercom and calling device for electromechanics, amplifiers for long-distance subscribers.
ATSC-100/2000
Coordinate automatic telephone exchanges are produced with a capacity that is a multiple of 100 numbers. The maximum capacity of stations is 9000 numbers.
The stations are equipped with separate cabinet units: AI – subscriber search; GI – group search; RI – register search.
II. Requirements for communication equipment for power supply devices.
SDPUPR
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.
^
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 pre-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.
^
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 the telegram sign, the CKS 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.
^
Processing of telegrams in the CKS
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, MSS-MSS.
Explain the format of the message when transferred from the OP to the MSC.
SECTION 5
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 contains 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 supplies malfunction, fuses blow, or the reception level of any TT channel decreases by 18 dB or the reception level in the TC channel by 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 design features of the transmitter
SECTION 6
Networks and data services
Topic 6.1 Organization of a radio packet data network
^
Characteristics and structure of the radio packet data transmission 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 structurally implemented 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 usually 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 to be filled out, but is highly recommended;
Finally, the large field below those listed above serves 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 application: 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 start, 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.
^
Postal 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
Features 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 Communications, 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.