JPS6360944B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a transmission path monitoring method, and in particular,
This paper relates to a transmission line monitoring method that is effective when applied to transmission lines for PCM signals and similar signals.

Conventionally, as a transmission line monitoring method, each repeater inserted and connected to the transmission line is equipped with a monitoring bandpass device with a unique frequency, and a special pattern such as an audio frequency band is returned from the outgoing path to the incoming path. method,
Alternatively, a system may be used in which audio signals are transmitted from each of the outgoing and incoming paths through the band waver to an intervening pair that exists separately from the signal line, or a logic circuit or latching may be used as a monitoring return circuit such as the band wave wave device. - A method is known in which a relay or the like is used to select a specific repeater using a special pattern of control pulses and close the return circuit for monitoring.

However, in these conventional monitoring systems, only a specific repeater performs loopback operation during monitoring, so each repeater must have its own monitoring loopback circuit. Furthermore, it is necessary to provide a logic circuit or the like for sequentially selecting folding circuits. Therefore, the repeater has a complicated monitoring circuit and is expensive. Moreover, the monitoring equipment at the terminal station for controlling these monitoring circuits also becomes complicated and expensive. Furthermore, since a specific repeater is monitored, as the number of repeaters increases, the number of repeater types increases, and it is difficult to realize a long-distance system due to limitations in the feasibility of monitoring circuits.

The object of the present invention is to provide a PCM which eliminates the aforementioned drawbacks.
An object of the present invention is to provide a method for monitoring transmission paths of digital signals such as signals.

According to the present invention, a simple switch circuit capable of connecting the output of an outgoing regenerative amplifier and the input of an incoming regenerative amplifier is arranged in each of a plurality of repeaters inserted and connected to a digital signal transmission path. The switch circuit is configured to receive a control signal different from the transmission signal and return a part of the closing signal during monitoring. Then, as a monitoring signal, the terminal station sends out a pulse train shorter than one round trip propagation time of each relay section at a cycle longer than one round trip propagation time of the entire length of the section to be monitored, and the pulse train is returned by the switch circuit. The pulse train is received by the terminal station, arranged on the time axis, and monitored.

The monitoring method of the present invention focuses on the propagation time of the cable between repeaters used in the transmission path, and uses a monitoring pulse train that is shorter than the return propagation time of each repeater section for one round trip propagation time of the entire length of the monitored section. If the pulse trains are sent from the terminal station at a longer period, the pulse trains returned from each repeater do not overlap on the time axis, and can be arranged sequentially for each return propagation time of the cable, starting from the repeater closest to the monitoring pulse train sending terminal station.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows the configuration of a PCM transmission system to which the monitoring system of the present invention is applied, and for the sake of simplicity, shows a case where monitoring is performed from one direction. Also, the second
FIG. 2a shows the monitoring pulse train P _S sent out from the terminal station, FIG. 2 b shows the received return pulse train P _R1 to P _Ro , and FIG. 2 c shows the details of the monitoring pulse train P _S of FIG. 2 a. The switch circuit 9 in FIG. 1 is configured to close upon receiving a control signal (sent from the terminal station 1) different from the transmission signal during monitoring. In FIGS. 1 and 2, the pulse train P _S sent out from the monitoring pulse transmitter 10 of the terminal station 1 is delayed by the propagation time T _C due to the outgoing cable 2 of the first relay section.
It reaches the first repeater 3. The pulse regenerated by the regenerative amplifier 8 of the first repeater 3 is transmitted to the switch circuit 9
(shown in FIG. 3), the pulse is divided into a folded pulse P _R1 and a pulse transmitted to the second repeater 4. P _R1 is turned back by the switch circuit 9, and the propagation time TC of the return cable 2 in the first relay section is delayed.
The signal reaches the folded pulse receiver 11 of the terminal station 1 with a delay of twice T _C (2T _C ) in total. Further, the pulse transmitted to the second repeater 4 is delayed by T _C in the outgoing cable 2 of the second repeater section, and is transmitted to the third repeater 5 as a return pulse P _R2 in the second repeater 4. The pulse is divided into P _R2 is turned back by the switch circuit 9 of the second repeater 4, and reaches the first repeater 3 with a T _C delay due to the return cable 2 of the second repeater section.
After being regenerated, the signal is delayed by T _C due to the return cable 2 in the first relay section, and reaches the return pulse receiver 11 . That is, after sending P _s , there is a delay of T _C (i.e., 4T _C ), which is four times the round-trip propagation time of the first and second relay sections.
It reaches the folded pulse receiver 11. At this time,
In order for the folded pulses P _R1 and P _R2 not to overlap in time, the transmission time T _P of the pulse train must be shorter than the round trip propagation time of one relay section (ie, 2T _C ). Hereinafter, the folded pulses P _R3 to P _Ro from the third repeater 5 onward reach the folded pulse receiver 11 at each round trip propagation time of each repeating section, in the same way as the above-mentioned P _R1 and P _R2 , and the time axis It can be arranged on t. In addition, when monitoring by continuously transmitting P _s , one round trip propagation time of the monitoring target section (i.e. 2T)
If the pulses are transmitted at the above period T _s (ie, T _s >2T), the return pulses from each repeater can be arranged without being affected by the transmitted pulses. By observing the folded pulses arranged in this manner, it is possible to grasp the status of each repeater and the transmission path as a whole. FIG. 3 shows the configuration of the switch circuit 9. In FIG. 3, 91 and 92 are input/output terminals for monitoring pulse trains, and 93 is an input terminal for control signals.

The embodiments shown in FIGS. 1 to 3 above are merely examples of the present invention, and it goes without saying that the present invention is not limited thereto. This includes the transformation of For example, in this embodiment, a case has been described in which monitoring is performed from one terminal station, but by increasing the function of the switch circuit, monitoring can be performed from either terminal station. Figures 4a and 4b show examples of the switch circuit 9 in the case of multi-system monitoring. Even when the number of systems increases, if the functions of the switch circuit 9 are increased as shown in Figure 4, it is possible to input the loop pulse receiver. All you have to do is connect it to the line you want to monitor. Further, a signal transmission line, a shielded line such as a cable, an intervening line, etc. can be used depending on the purpose for transmitting control signals to the switch circuit 9, and an effective monitoring system can be constructed. In addition, even in the monitoring equipment of the terminal station, by appropriately selecting the input/output points of the monitoring signal, monitoring can be performed using the minimum number of measuring instruments such as a pulse generator and an oscilloscope.

As explained above, the present invention makes it possible to make the repeater easy to handle, highly reliable, and inexpensive by unifying the types of monitoring circuits in the repeater. This has the effect that it is possible to monitor transmission lines with monitoring equipment, and also to monitor long-distance systems.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a PCM transmission line to which the monitoring method of the present invention is applied. FIG. 2 is a time chart showing the temporal relationship of pulses in each part of FIG. 1, where a is a monitoring pulse train sent from a terminal station,
b shows the return pulse train received at the terminal station, and c shows details of the monitoring pulse train _Ps of a. FIG. 3 is a circuit diagram showing the configuration of the switch circuit 9 of FIG. 1. FIGS. 4a and 4b are circuit diagrams showing switch circuits for monitoring multiple systems, respectively. 1, 12...terminal station, 2...cable, 3-7...repeater, 8...regenerative amplifier, 9...switch circuit, 10...
Monitoring pulse transmitter, 11... Return pulse receiver, T _c ... Propagation time of one repeater section, T... Propagation time from the terminal station to the farthest end repeater, T _P ... Sending time of the sending pulse train, T _s ... Sending out Period of pulse train, P _s ...
Sending pulse train, P _R1 , P _R2 , P _R3 , P _R4 , P _Ro ... return pulse train from the repeater, 2T ... one round trip propagation time of the entire length of the monitored section, 2T _c ... round trip propagation time of one repeater section.

Claims (1)

[Claims] 1. In a digital signal transmission path monitoring system, a portion of the signal is transmitted between the output of a regenerative amplifier on the outgoing path and the input of the regenerative amplifier on the inbound path to each of a plurality of repeaters inserted and connected to the transmission path. A switch circuit that can be connected back is arranged, and the switch circuit is configured to close upon receiving a control signal different from the transmission signal during monitoring, and the control signal is transmitted from the terminal station to the plurality of repeaters. Along with sending out
As a monitoring signal, a pulse train shorter than one round trip propagation time of each repeater section is sent out at a cycle longer than one round trip propagation time of the entire length of the section to be monitored, and the switch circuit of each of the plurality of repeaters is A method for monitoring a transmission path, characterized in that the terminal station receives and monitors the pulse train returned through the switch circuit during a time when the switch circuit is closed by the control signal.