JPS5920304B2 - Fault repeater search method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a faulty repeater search method that makes it possible to search for faulty repeaters on a PCM transmission line with a simple configuration.

In long-distance transmission lines, repeaters are maintained at predetermined distances to regenerate and relay transmitted signals, so even if a failure occurs in any one repeater, signal transmission will be completely interrupted. Or the error rate will increase abnormally.

Therefore, there is a need to quickly identify and repair faulty repeaters. For this reason, various repeater failure detection methods have already been proposed. For example, JP-A No. 55-60363 or JP-A No. 5
As shown in Publication No. 5-60364, a repeater is equipped with a signal disconnection detector, a clock oscillator, a frequency divider, a memory, etc., and a signal with a specific pattern predetermined for the repeater is transmitted by fault detection. A faulty repeater is identified by receiving this specific pattern of signals at the terminal station. However, since the scale of the circuit added to the repeater increases, problems arise in terms of reliability, economy, power consumption, etc. An object of the present invention is to facilitate the search for a faulty repeater by adding a small amount of configuration. Examples will be described in detail below. The figure is a block diagram of the main parts of an embodiment of the present invention, where IN is an input terminal, OUT is an output terminal, EQ is an equalization amplifier, AGC is an automatic gain control circuit, DET is a signal abnormality detection circuit, and TM is a timing extraction circuit. The circuit, SAWFIL is a surface acoustic wave filter that constitutes a bandpass filter, LIMAMP beam transmitter amplifier, PS is a phase shift circuit, G is an AND gate circuit, REG is an identification regeneration circuit, and SV is an additional circuit added for searching for faulty repeaters. It is. In a normal case, the PCM signal applied to the input terminal IN is amplified to a constant level by the equalization amplifier EQ and the automatic gain control circuit AGC, and then applied to the identification and regeneration circuit REG.
The identification reproducing circuit R synchronizes with the timing signal extracted by
A PCM signal is sent from EG to the next repeater or terminal station via the output terminal OUT.

A failure occurred in the previous repeater or transmission, and the input terminal was disconnected.
When the level of the PCM signal applied to the signal is abnormally reduced or cut off, the gain of the automatic gain control circuit AGC becomes maximum, and the output of the equalization amplifier EQ contains a lot of noise or becomes only noise. The signal abnormality detection circuit DET detects such reduction or interruption of the input signal, and can determine that an abnormality occurs when the AGC voltage exceeds a predetermined level, for example. The AND gate circuit G is opened by this abnormality detection. When the AND gate circuit G is opened, the surface acoustic wave filter S of the timing extraction circuit TM
AWFIL, limiter amplifier LIMAMPl addition circuit S
A loop of the AND gate circuit G1 and the phase shift circuit PS is formed, and the output of the limiter amplifier LIMAMP is passed through the phase shift circuit PS- to the surface acoustic wave filter SAWF.
Returned to IL.

Therefore, a surface acoustic wave oscillator is formed, and the oscillation frequency is determined by the phase shift circuit PS and the surface acoustic wave filter SA.
It is almost determined by the WFIL, and can be stably oscillated even in the hundreds of MHz band. In this case, the oscillation band is equal to the passband of the surface acoustic wave filter SAWFIL, and the oscillation frequency is near the clock frequency. Furthermore, the oscillation frequency can be changed by changing the phase using the phase shift circuit PS. Therefore, the oscillation frequency can be varied by adjusting the phase by the phase shift circuit PS corresponding to the repeater. In the event of an abnormality, the regeneration circuit RE identifies the noise output of the equalization amplifier EQ using a clock frequency compatible with the repeater.
Since the signal is reproduced by G, a random pattern signal is sent out, and since the subsequent repeater also uses the same surface acoustic wave filter SAWFIL, this random pattern signal can be relayed without error.

Since the terminal station receives the above-mentioned random pattern signal at the time of a failure, the clock component is extracted by a timing extraction circuit or the like, and the occurrence of a failure can be identified by detecting that the extracted clock frequency is different from the normal time.

Furthermore, since the clock frequency is unique to each repeater, a faulty repeater can be immediately identified by detecting the frequency using a frequency counter or the like. Although this is simple and can be miniaturized, it is also possible to use a bandpass filter constructed from other elements.

It can also be applied to optical PCM transmission systems,
In that case, photoelectric conversion and electro-optical conversion means will be provided. Further, the AND gate circuit G can also be an analog switch. As explained above, in the present invention, the additional circuit SV added to the repeater is composed of the signal abnormality detection circuit DET, the phase shift circuit PSL, and the AND gate circuit G, and the timing extraction circuit TM is used to perform relaying in the event of a failure. It is possible to generate a clock frequency corresponding to the device.

Furthermore, at the terminal station, it is possible to search for a faulty repeater simply by connecting a frequency counter or the like to the timing extraction circuit. Therefore, by adding a small amount of configuration to the repeater, it is possible to easily search for a faulty repeater, which improves reliability and economical efficiency, and provides benefits such as lower power consumption. be.

[Brief explanation of the drawing]

The figure is a block diagram of an embodiment of the present invention.

Claims (1)

[Claims] 1 In a faulty repeater search method for a PCM transmission line, the repeater includes an input signal reduction or disconnection detection circuit, a timing extraction circuit having a bandpass filter, a phase shift circuit, and the output of the detection circuit detects the timing. A gate circuit is provided to feed back the output of the extraction circuit via the phase shift circuit, and the phase shift circuit enables oscillation of a clock frequency compatible with the repeater, and in the event of a failure, sends out an oscillation signal of the clock frequency, and A faulty repeater search method characterized in that a faulty repeater is identified at a station based on the clock frequency.