JPS59163929A - Supervisory system for relay transmission line - Google Patents

Abstract

PURPOSE:To attain sure retrieval of improper contactness of a connecting point of coaxial cables by superimposing a failure position retrieval signal provided between adjacent channel bands on a low frequency band of a relay transmission line. CONSTITUTION:A failure position retrieval signal band 14 provided at the low frequency region of a transmission line band 13 causes attenuation 16 at a coaxial cable connection defective point more remarkably than that of a high frequency failure location retrieval signal band 15. The attenuation 16 at a connection defect point 8 of a low frequency failure location retrieval signal 2 of a repeater 5 is detected by a relay transmission line supervisory circuit 10 of a station 9 at receiving terminal. On the other hand, low frequency failure location retrieval signals 3, 4 of repeaters 6, 7 are detected respectively at a normal level by relay transmission line supervisory circuits 11, 12. Thus, the coaxial cable connection defective point 8 is detected surely from the result.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a relay transmission line monitoring method in which when a fault occurs in a relay transmission line, a receiving end station detects a change in the level of a fault location search signal output from each repeater. It is.

The conventional relay transmission line monitoring method is performed by inserting a fault location search signal using a high frequency in the transmission line frequency band into the input of each repeater, and monitoring the reception level at the receiving end station. According to this method, if a connection failure occurs at the connection point of the coaxial cable that causes the connection to become slightly disconnected, the fault location search signal at the receiving end station will be abnormal because the fault location search signal has a high frequency and the spatial transmission loss is small. level may not be received. As a result, there was a drawback in that a coaxial cable connection point failure could not be detected at the receiving end station.

SUMMARY OF THE INVENTION An object of the present invention is to provide a relay transmission line monitoring system that can reliably search for connection failures in coaxial cables.

The relay transmission line monitoring system of the present invention is provided at each input of a repeater that is cascaded to constitute a relay transmission line, and is installed between adjacent communication line bands located in the low frequency band of the relay transmission line. The relay transmission path is monitored by superimposing a fault location search signal on the fault location search signal, and detecting an abnormality in the level of the fault location search signal output from the repeater at a receiving terminal station.

This will be explained below with reference to the drawings.

FIG. 1 shows a general relay transmission line monitoring system. 1 is a transmitting terminal station. When a coaxial cable connection failure point 8 occurs, the reception terminal station 9 can receive the fault location search signals 3 and 4 up to the repeaters 6 and 7. However, the fault location search signal 2 from the repeater 5 cannot normally be received. This allows the coaxial cable connection failure point 8 to be searched for. The receiving terminal station 9 includes relay transmission path monitoring circuits 10, 11.12 that monitor level changes in the fault location search signal 43.4. The relay transmission path monitoring circuit 10 monitors changes in the level of the fault location search signal 20.

The relay transmission path monitoring circuit 11 monitors changes in the level of the fault location search signal 30. Similarly, the relay transmission path monitoring circuit 1
2 monitors the level change of the fault location search signal 40.

In the event of the above-mentioned failure, the relay transmission line monitoring circuit 10 detects the υ coaxial cable connection failure point 8 because the input failure location search signal 2 normally disappears.

The other relay transmission line monitoring circuits 11 and 12 can receive the normal fault location search signals 3 and 4. However, since the fault location search signal 2 is positioned in the high range 15 of the transmission line frequency band 13 in the transmission line frequency temporal characteristic 17 at the coaxial cable connection point in FIG. 2, it may not be attenuated at the coaxial cable connection fault point 8. . To be sure of this, the receiving terminal station 9 receives the fault location search signal 2 at a normal level, and even if a coaxial cable connection failure point 8 occurs, it will judge it as if it were normal.

As shown in FIG. 2, the fault location search signal band 14 provided in the lower range of the transmission path band 13 is more markedly attenuated than the high frequency fault location signal band 15 at the low frequency fault location signal band 16 at the coaxial cable connection fault point. occurs. The attenuation 16 of the low frequency fault location search signal at this coaxial cable connection failure point i is detected by the relay transmission line monitoring circuit 10 of the receiving terminal station 9. On the other hand, the fault location search signals 3 and 4 from the repeaters 6.7 are detected at normal levels by the relay transmission line monitoring circuits 11 and 12. From the above results, coaxial cable connection failure point 8 is detected.

FIG. 3 shows the frequency 18.4 of the fault location search signals 2, 3.4 provided in the lower frequency band of the transmission line in the embodiment of the present invention.
19.20 is shown. Fault location search signal frequency 18.19
．． 20 is provided in an unused frequency band between communication path bands 21, 22, 23, etc. which are lower in the transmission path frequency band 13.

As described above, according to the present invention, it is possible to reliably detect a coaxial cable connection failure point in a relay transmission path.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a general relay transmission line monitoring system.
FIGS. 2 and 3 are characteristic diagrams and layout diagrams showing embodiments of the present invention. 1... Transmission terminal station, 2, 3.4... Fault location search signal, 5, 6.7... Repeater, s...
... Coaxial cable connection failure point, 9 ... Receiving terminal station, 10, 11.12 ... Relay transmission line monitoring circuit, 13 ... Transmission line frequency band, 14...
...Low frequency fault location search signal band, 15...High frequency fault location signal band, 16...Attenuation of low frequency fault location search signal at a poor coaxial cable connection point, 17
...Transmission line frequency characteristics at the coaxial cable connection failure point, 18, 19.20... Frequency of low frequency fault location search signal, 21, 22.23... Communication path band.

Claims (1)

[Claims] At each input of the repeaters that are connected in cascade to form a relay transmission line,
superimposing a fault location search signal located in a low frequency band of the relay transmission path and provided between adjacent communication channel bands, and receiving a level abnormality of the fault location search signal output from the repeater; 1. A relay transmission line monitoring system, characterized in that the relay transmission line is monitored by detection at a terminal station.