RU2037875C1 - Device for interface between computer and telephone communication line - Google Patents

Abstract

FIELD: computer engineering. SUBSTANCE: device has channel transceiver 6, address decoding unit 7, channel transmitter 8, data register 9, input and output optical matching units 10 and 11, comparator 12, band-pass filter 13, surge noise protection unit 14, voltage conversion unit 15, commutation unit 16. Constant voltage level in telephone line is used for power supply of band-pass filter, comparator and units 10, 11, 14 and 15. EFFECT: communication speed is 1200 bits per second. 6 dwg

Description

 The invention relates to computer technology and is intended for interfacing personal computers via dial-up or dedicated telephone communication channels.

 The aim of the invention is to reduce hardware costs.

 In FIG. 1 shows an example application of the device; figure 2 structural diagram of the device; in FIG. 3 example implementation of a block of protection against impulse noise; in FIG. 4 file transfer algorithm; 5 and 6 are timing diagrams of the device.

 The local distributed computer network (Fig. 1) consists of N personal computers 1, devices 2 for connecting computers to the telephone line, telephone sets 3 and an office automatic telephone exchange 4.

 A device 2 for connecting a computer to the telephone line is connected to the computer channel 5 (figure 2) and contains a channel transceiver 6, an address decryption unit 7, a channel transmitter 8, a data register 9, an input optical matching unit 10, an output optical matching unit 11, a comparator 12, a bandpass filter 13, an impulse noise protection unit 14, a voltage conversion unit 15, and a switching unit 16. Block 14 (figure 3) contains capacitors 1719 and diodes 20 and 21.

 The device provides data transmission via two-wire dial-up or dedicated channels of an institutional telephone network or a public network with a speed of up to 1200 bit / s. Transmission is carried out in a synchronous sequential manner in half-duplex mode using the Manchester modulation code.

 The interaction of two computers during file transfer is shown in figure 4. A communication session begins with establishing a connection over a communication channel. After that, one computer is transferred to the master mode, and the other to the slave. Further exchange management is carried out from the host computer.

 Information exchange between computers is carried out in file exchange mode. Moreover, all actions for organizing file exchange are performed programmatically, the device provides a physical interface level.

 In the initial state, the switching unit 16 is installed in a position that provides a physical channel between the telephone 3 and the telephone line of the PBX 4. In order to carry out file exchange with any of the computers on the network, the computer user picks up the telephone receiver of his telephone and establishes a physical channel with free currently another user. Computer addresses correspond to the subscriber numbers of the telephone network. Having established a physical channel through the PBX between two telephone sets and having agreed on information exchange, users install the switching units 16 of their devices in the position connecting the computer to the telephone network. In this case, the station voltage from the input / output of the telephone line through block 16 enters the voltage conversion block 15 and provides the specified voltage from the input voltage output to the input 10 and output 11 optical matching blocks, a comparator 12, a bandpass filter 13, and an impulse noise protection block 14 , thereby preparing the listed blocks for work in the exchange mode. The supply voltage to the data register 9, the channel transmitter 8, the address decryption unit 7, the channel transceiver 6 is supplied from the computer power supply.

 Reception mode. In normal operation (in the absence of interference), the input signal is received from the telephone line through block 16 and the voltage conversion block 15 to the information input of the impulse noise protection block 14, which protects the input of the bandpass filter 13 from high-voltage interference (interference signal above 0.7 V ) and then passes to the output of the band-pass filter 13, which extracts a useful signal from the signal coming along the line with a passband of 600-2000 Hz. From the output of the bandpass filter 13, the signal enters through the information input to the comparator 12, which restores the rectangular shape of the signal and passes the signal to the input of the input optical matching unit 10, which provides galvanic isolation of the telephone line of the computer and converting the level of the input signal to the level received in the computer. From the output of the input optical matching unit 10, the input signal enters the discharge register 9 data. Reading this signal from the register 9 data is carried out according to the standard procedure for reading computers.

 From the computer via the address bus to the channel 5 of the computer receives the address of the register 9 data. This address is decrypted by the address decryption unit 7 and a signal is received at the input of the channel transceiver and data register 9, which allows reading data from the register. Reading data from the data register 9 is carried out by the read signal coming from the channel 5 of the computer through the channel transmitter 8.

 If there is interference in the input signal, if it falls into the spectrum of the useful signal (600-2000 Hz), if its level is less than half the level of the input signal, this interference is ignored, since the comparator 12 does not perceive it, and if the interference level is more than half the level of the useful signal, it passes through the comparator 12 and blocks 10, 9 and 6 into the channel 5 of the computer and is detected by the software method of integration of the input signal. Moreover, if the interference duration is less than 200 μs, then it is recognized by the program, and if more than 200 μs, then the interference is perceived as a useful signal and error detection is carried out by the next software level when analyzing the received data block. The timing diagram of the operation of the interface device during data entry is shown in Fig.5.

 Output mode. The output is transmitted from the computer to the telephone line bit by bit. The computer sets the address of the data register 9 on the bus channel address 5 of the computer, and the transmitted bit on the data bus channel 5 of the computer. From the outputs of the address decryption unit 7, the input of the channel transceiver 6 and the first input of the data register 9 receives signals that allow the passage of a data bit to the input of the data register 9, preparing it for reception.

 The output data bit is recorded in the data register 9 by a write signal coming from the computer channel 5 through the channel transmitter 8 to the input of the data register 9.

 From the output of data register 9, the data bit is fed to the output optical matching unit 11, which provides both galvanic isolation of the computer output and the telephone line, and conversion (attenuation) of the signal level to the level accepted by the International Advisory Committee on Telephony and Telegraphy for tonal frequency channels. From the output of block 11, the output information signal through voltage converting block 15 and block 16 enters the telephone line. The timing diagram of the operation of the interface device when outputting data is shown in Fig.6.

Claims (1)

 DEVICE FOR CONNECTING A COMPUTER TO A TELEPHONE COMMUNICATION LINE, containing an address decryption unit, a data register, a channel transceiver, a channel transmitter, a switching unit, a voltage conversion unit, a comparator, a bandpass filter, the first input-output of the switching unit is connected to the telephone line, the second input is the output of the switching unit is the input-output of connecting the telephone, the third input-output of the switching unit is connected to the information input-output of the voltage conversion unit, the output of the bandpass filter with Din is with the information input of the comparator, the first and second information inputs and outputs of the channel transceiver are connected to the information inputs and outputs of the device and the data register, respectively, the selection input of which is connected to the first output of the address decryption unit, the second output of which is connected to the control input of the channel transceiver, the input of the block the address decryption is connected to the address input of the device, the read-write input of the data register through the channel transmitter is connected to the read-write input of the device, from characterized in that, in order to reduce hardware costs, it contains an input and output optical matching blocks and a protection block from impulse noise, the first output of the voltage conversion unit is connected to the information input of the pulse protection block, the output of which is connected to the information input of the bandpass filter, the output of the comparator is connected to the information input of the input optical matching unit, the output of which is connected to the information input of the data register, the output of which is connected to the information input m output optical matching unit, an output of which is connected to the data input of the voltage conversion unit, the second output of which is connected with the inputs for connecting the power input and output optical matching blocks comparator, a bandpass filter and protect the unit against impulse noise.

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