JPS5947904B2 - Dual transmission communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dual transmission communication system that improves the reliability of important communication lines by simultaneously transmitting the same signal to two transmission lines.

It is well known that many companies, government offices, etc. currently use a large number of dedicated communication lines borrowed from Nippon Telegraph and Telephone Corporation lines to transmit not only telephone calls but also facsimiles, data, and even television.

Some of these lines include lines that carry important communications for air traffic control, security maintenance, etc., and if they become impaired, it could endanger human life or cause social chaos. Naturally, there are cases where the person using each dedicated line prepares a backup line, but there are also cases where no backup line is provided. In consideration of social trust, the provider of the line (Indo Telegraph and Telephone Public Corporation) has constructed its own transmission line in a double configuration, and in the event of a failure of the working line, it immediately switches automatically or manually to the backup line. It's summery. However, this switching requires a person with a certain degree of skill, and if either the transmitting terminal station or the receiving terminal station is unmanned, this switching is impossible and the line will be disconnected. Therefore, from the point of view of increasing reliability, it is first considered to use complete duplex transmission.

That is, as shown in FIG. 1, a transmitting end 1 and a receiving end 2 are connected by parallel transmission lines 3 and 4. In this way, even if one of the transmission lines becomes a failure, it is almost impossible for the other transmission line to become a failure at the same time, so the line can be maintained. However, with this configuration, if one line is disconnected, the reception level at the receiving end 2 will be lower than normal, and the fidelity of the reproduced signal will be significantly lowered. In order to eliminate this drawback, for example, as shown in FIG.
4. It is known that A/D converters 5 and 5' are inserted into each receiving side to digitize the signals, which are synthesized in an OR circuit 6, and then converted into analog signals again by a D/A converter 7. It is being In this case, there is a feature that even if either of the working and protection transmission lines 3 and 4 becomes impaired, no instantaneous interruption or level fluctuation occurs at all. However, on the other hand, the phase of the signals on both transmission lines may vary due to the difference in the physical length of the active and backup transmission lines, or the difference in the frequency of the carrier wave at both transmitting and receiving ends since it is generally a carrier circuit in the case of a long-distance transmission line. In general, they do not match, and a means to make them match is required, which is also technically difficult. The present invention eliminates the above-mentioned drawbacks, except for slight momentary interruptions. In other words, it provides a dual transmission communication system that does not involve level fluctuations and in which the phase difference between the signals on both transmission paths is not a problem. .

This will be explained in detail below using the drawings. FIG. 3 shows the principle of this invention.

According to this invention, on the receiving side, each signal from the working transmission line 3 and the backup transmission line 4 is supplied as a digital signal to the pulse regenerator 8 having an automatic threshold control function. Therefore, if the transmission signal is an analog signal, each transmission line 3,
A/D converters 5 and 5'' are respectively inserted on the receiving side of 4 to convert the signal into a digital signal.The digital signal from the backup transmission line 4 is supplied to the pulse regenerator 8 through an attenuator 10. The response width of the automatic threshold control function of the pulse regenerator 8 is made sufficiently wide, and the attenuator 10
Under normal conditions, in which the digital signal from the A/D converter 5 is supplied to the pulse regenerator 8, the A/D converter 5 is adjusted.
The input to the pulse regenerator 8 of the D converter 5'' is an A/D
The input threshold value of the converter 5 to the pulse regeneration repeater 8 is below the threshold value, but since the output of the A/D converter 5 exists, the threshold value of the pulse regeneration repeater 8 decreases, and the input to the A/D converter 5 Pulse regeneration relay using the output. It is assumed that the attenuation amount of the attenuator 10 and the automatic threshold control function of the pulse regenerator 8 are selected so that the attenuator 8 operates satisfactorily. Note that the pulse regenerator 8 having an automatic threshold control function is conventionally known and is used, for example, in PCM multiplex communication. According to the configuration shown in FIG. 3, when the working transmission line 3 is normal, the protection transmission line 4
Regardless of the state of The signal is converted back to an analog signal by the D/A converter 7 and reaches the receiving end 2. Now, if we consider the case where the current transmission line 3 is disconnected, the input of the A/D converter 5 becomes O, and therefore its output also becomes O. Therefore, the pulse regeneration threshold of the pulse regeneration repeater 8 decreases with a certain time constant,
Finally, the pulse of the output of the attenuator 10 is regenerated. At this point, the signal to the receiving end 2 has been transmitted through the backup transmission line 4, and during this time there will be some signal interruption time due to the time constant of the pulse regenerator 8, but this is true even if it is a telephone line. It's not a problem at all. Although the analog transmission line has been described above, it is even more convenient if this is a digital transmission line. Is the digital transmission line originally as shown in Figure 4? At the receiving end 1, the signal is converted into a digital signal by the A/D converter 5 and sent to the transmission line 3, and at the receiving end, the signal is converted back to an analog signal by the D/A converter 7 and reaches the receiving end 2. The digital transmission path 3 can be diversified with an appropriate degree of multiplicity by an appropriate method as necessary. Moreover, in the digital transmission line 3, the pulses of the digital transmission line are sent out to a certain extent even if there is no signal from the transmitter 1 due to the necessity of timing and the like. FIG. 5 shows an example in which the present invention is implemented using such a digital transmission line.

After the signal from the transmitting end 1 is converted into a digital signal by the A/D converter 5, it is sent to both the working transmission line 3 and the protection transmission line 4, and the signal from the working transmission line 3 is sent to the receiving side 2 as is. The signal from the backup transmission line 4 is supplied to the pulse regeneration repeater 8 through an attenuator 10. The output is converted into an analog signal by the D/A converter 7 and reaches the receiving end 2. FIG. 6 shows an example in which the present invention is applied to the PCM-24B system which is currently in practical use.
The output side of the A/D converter (PCM terminal device) 5 on the transmitting side is connected to the active transmission line 3 through the input side (SIN) of the transmitting terminal relay device 8 and further through the distribution panel 11, and is also connected to the active transmission line 3 for backup transmission. The working transmission line 3 and the protection transmission line 4 are connected in parallel by connecting to the input side (SIN) of the terminal relay device 8'' of the line 4. On the receiving side, the working transmission line 3 and the protection transmission line 4 are Pulse regenerators 9 and 9 via distribution boards 11'', respectively.
'' is connected to the output side (ROUT) of the distribution panel 11.
'', the working transmission line 3 and the protection transmission line 4 are connected to each other via the attenuator 10. Under normal conditions, the signal from the transmitting end 1 is always connected to the working transmission line 3 and the protection transmission line 4. Therefore, the attenuator 10 normally operates so that the signal on the backup transmission line 4 is below the threshold value on the working transmission line 3.
In addition, the attenuator 10 shall be adjusted so that the pulse regeneration repeater 9 (end station repeater) can be sufficiently operated when the signal on the current transmission line 3 is cut off. Note that the capacitor of the attenuator 10 is used to interrupt direct current since direct current is superimposed on the transmission lines 3 and 4. When the working transmission line 3 is normal, the signal from the transmitting end 1 is transmitted through the working transmission line 3 via the transmitting end station repeater 8 regardless of the parallel connection (sending side), and then the signal from the receiving end The signal reaches the receiving end 2 via the station relay 9 and the D/A converter 7. Even if the working transmission line 3 is disconnected, the working and protection transmission lines 3 and 4 are always connected in parallel, so the signal from the transmitting end 1 is transferred to the transmitting terminal relay device 8''.
The pulse is then transmitted through the backup transmission line 4 , passed through the attenuator 10 , is regenerated by the receiving side terminal repeater 9 , passes through the D/A converter 7 and reaches the receiving end 2 . As described above, according to the communication system of the present invention, the signal obtained at the receiving end 2 is only from one of the working and backup transmission lines, so differences in phase, level, etc. between these two transmission lines are taken into consideration. At first glance, it can be expected that parallel transmission lines will improve reliability.

In PCM-24B system lines, the pulse regeneration repeater at the receiving end station has an automatic threshold control function with a sufficiently large response width, so by creating only a simple attenuator, one end station or both end stations can be It is possible to significantly improve the reliability of lines that are important in social life such as police lines and fire lines housed in unmanned stations, as well as other important lines, and also to save labor on maintenance. can contribute.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a general duplex transmission system, Fig. 2 is a block diagram showing a conventional duplex transmission system that eliminates the drawbacks of Fig. 1, and Fig. 3 is a duplex transmission communication system according to the present invention. 4 is a diagram showing the basic configuration of the digital transmission system, FIG. 5 is a block diagram when this invention is applied to a digital line, and FIG. 6 is a diagram showing the basic configuration of the digital transmission system.
FIG. 2 is a diagram showing an example when applied to the -24B system. 1: Transmitting end, 2: Receiving end, 3: Working transmission line, 4: Backup transmission line, 5, 5'': Analog-digital converter, 6: OR circuit, 7: Digital-analog converter, 8, 8'', 9 ,9
″: Pulse regenerator with automatic threshold control function, 1
0: Attenuator, 11,11″: Distribution board.

Claims (1)

[Claims] 1 A protection transmission line independent of one working transmission line is connected in parallel, and signals are always sent in parallel to these working transmission lines and protection transmission lines on the transmitting side, and signals are always sent in parallel to the working transmission line and the protection transmission line on the receiving side. The signal from the backup transmission line is supplied as a digital signal to the pulse regeneration repeater having an automatic threshold control function, and the signal from the backup transmission line is supplied as a digital signal to the pulse regeneration repeater through an attenuator, If the line is normal, the digital signal from the backup transmission line will be below the threshold value of the working transmission line at the pulse regeneration repeater, and if the signal on the working transmission line is disconnected, the digital signal from the protection transmission line will pass through the pulse regeneration repeater. The attenuation amount of the attenuator is selected such that the threshold value of is lowered and the pulse of the backup transmission line exceeds the threshold value.