JPS6276991A - Circuit supervisory unit - Google Patents

Abstract

PURPOSE:To accurately grasp the occurrence of a failure at each home terminal equip ment and to discriminate the place of the failure by providing a means that decides in which branch of a transmission path the failure has occurred to a supervisory terminal equipment when a failure detection signal from a tap-off having a failure detector that detects the abnormality of a down transmission signal is received. CONSTITUTION:Each of tap-offs 50-58 is equipped with the failure detector that detects the abnormality of the down transmission signal in its inside. When the failure is generated at, for example,a branch 32 out of branches 30-49, (the occurrence of the failure at nodes 71-75 is considered as the failure at the branch to which the node is connected) the failure is detected at tap-offs 54-57 connected to the branch 32. When the failure is detected, the tap-off transfers the failure detection signal of the tap-off to the supervisory terminal of a head end 25 as an up transmission signal. The failure detection signal is demodulated at a reception demodulation circuit 17 in the supervisory terminal, being sent to a control circuit 20. At a storage device 26, a corresponding table between each branch of the transmission paths and the terminal equipment that is connected to each branch and is equipped with the failure detector is stored, and the control circuit 20 discriminates the branch where the failure is generated while using the corresponding table.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a line monitoring device for monitoring faults occurring in a dendritic wired transmission network such as a CATV transmission system.

Conventional technology CATV in Japan began as a shared viewing system to prevent viewing difficulties, but recently there are signs that systems such as urban CATV are becoming larger-scale. As the scale of the system increases, maintenance and inspection problems become a problem. Especially the transmission system,
Relay amplifiers, which are particularly prone to failure, are scattered over a wide area, so it often takes time to restore them when a failure occurs. On the other hand, if billing information such as pay television services and information about various security systems are to be transmitted over the same line, this transmission system is required to have even higher reliability.

In order to improve the reliability of a transmission system, it is necessary to improve the reliability of each component, discover failures early, and shorten the time until recovery by recognizing the location of the failure. It is important to keep it to a minimum. Such functions are realized by a line monitoring device capable of remote monitoring.

Regarding line monitoring devices that can be remotely monitored,
Conventionally, fault detectors are installed in relay amplifiers, and these fault detectors have unidirectional or bidirectional communication functions, and data is exchanged between each fault detector and a monitoring terminal installed at the head end, etc. , a common method was to monitor the status of relay amplifiers.

An example of the above-mentioned conventional line monitoring device will be described below with reference to the drawings.

FIG. 8 shows an example of a CATV transmission network.

In Figure 8, 25 is the head end, 60.61.6
2 is a relay amplifier, 63 is a tap-off, 64.65 is a termination device, 68 is a terminal device, and 69 is a receiver. A downlink transmission signal such as a sharp signal is sent from the head end 25, and enters a terminal device 68 in each home via, for example, a relay amplifier 60, a relay amplifier 62, and a tap-off 63, and is descrambled if scrambled. and enters the receiver 69.

In the conventional line monitoring device, a fault detector is placed in the trunk relay amplifier 60, 61, and a monitoring terminal is placed in the head end 25. FIG. 9 shows a circuit diagram of a relay amplifier equipped with a fault detector. Further, FIG. 10 shows a circuit configuration diagram of a head end in which a monitoring terminal is located.

In FIG. 9, 2.6 is an upper and lower signal separation filter, 11
1 is a branching filter, 12 is a multiplexer, 3 is a down line amplifier, 4 is an up line amplifier, 98 is a control circuit, 9 is a reception demodulation circuit, 1
0 is a transmission modulation circuit, 1 is an input terminal, 7 is an output terminal, and the above constitutes a bidirectional relay amplifier lOO.

On the other hand, in FIG. 10, 19 is a transmission modulation circuit, 17 is a reception demodulation circuit, 20 is a control circuit, 21 is a printing device, and 22
1 is a display device, 23 is a keyboard, 15 is a multiplexer, 16 is a demultiplexer, 14 is an upper and lower signal separation filter, and the monitoring terminal 24 is constituted by the above. 18 is a transmitting/receiving device, and the head end 2 is connected to the monitoring terminal 24 and the transmitting/receiving device 18.
5 is configured, and 13 is a head end output terminal.

The operation of the line monitoring device configured as described above will be briefly explained below with reference to FIGS. 9 and 10.

Signals indicating the status of the down line amplifier 3 and up line amplifier 4 (for example, the output level of each amplifier) are sent to the control circuit 9.
8 is input. On the other hand, the control circuit 20 of the monitoring terminal 24 uses the modulation transmission circuit 19 and the multiplexer 15 to send out a downlink command. This downlink command is transmitted to the repeater amplifier 100 like other downlink signals, and is decoded by the control circuit 98 of the repeater amplifier 100 using the duplexer 11 and the reception demodulation circuit 9. In response to the downlink command, the transmit modulation circuit 10. Using the multiplexer 12, the control circuit 98 sends the states of the downlink amplifier 3 and uplink amplifier 4 to the transmission line as an uplink command. This uplink command is transmitted to the head end 25 and decoded by the control circuit 20 using the duplexer 16 and the reception demodulation circuit 17. In the case of CATV transmission, uplink signals and downlink signals are frequency multiplexed, and usually the high band is used for the downlink signal and the low band is used for the uplink signal. The upper and lower signal separation filters 2, 6.14 separate the upper and lower signals 43 using such a difference in frequency.

As described above, by performing bidirectional communication between the control circuit 9 of each relay amplifier and the control circuit 20 of the monitoring terminal, the control circuit 20 of the monitoring terminal can grasp the status of each relay amplifier. When a request is made from the keyboard 23 or an abnormal state is discovered, the state is displayed on the display device 22 and the printing device 21, thereby enabling early recovery. Further, depending on the type of signal input to the control circuit 8 (for example, temperature, etc.), failures can be predicted and prevented.

(Japanese Unexamined Patent Publication No. 56-158584) Problems to be Solved by the Invention However, in the above configuration, if a fault detector is installed in every relay amplifier, the number of fault detectors will increase, which will increase the cost. There are drawbacks. For this reason, in conventional transmission systems, fault detectors are installed only in main relay amplifiers such as trunk lines, but this cannot detect faults in relay amplifiers near the end of the transmission network, that is, in terminal devices in each home. The problem was that it was not possible to accurately grasp the occurrence of failures.

In view of the above-mentioned problems, the present invention provides an inexpensive line monitoring device that can accurately grasp the occurrence of a failure in each home terminal device and determine the location of the failure.

Means for Solving the Problems In order to solve the above problems, the line monitoring device of the present invention has the following features:
At the end of each branched transmission path of the transmission system,
A tap-off having a fault detector for detecting an abnormality in the downlink transmission signal, a means for transmitting and concentrating the fault detection signals from these tap-offs to a monitoring terminal, and a means for transmitting and concentrating fault detection signals from these tap-offs to a monitoring terminal, and a means for transmitting and transmitting fault detection signals from these tap-offs to a monitoring terminal, A storage means that stores a correspondence table with these tap-offs connected to the tap-off, and when a failure detection signal is received from these tap-offs, this correspondence table is used to determine which transmission route technique a failure has occurred. It is equipped with the means.

Function: With the above-described configuration, the present invention detects a fault at the end of the transmission network, so that the occurrence of a fault can be accurately detected. In addition, fault detection signals from tap-offs equipped with fault detectors are transmitted centrally to a monitoring terminal, and using a correspondence table between each branch of each transmission path and these tap-offs connected under each, it is possible to determine which transmission path is connected. It is possible to identify whether a fault has occurred on a branch.

Furthermore, with the configuration of the line monitoring device of the present invention, compared to the conventional line monitoring system in which all relay amplifiers have fault detectors, even if the number of fault detectors is small, it has the same fault detection ability, so it is cheaper. system can be realized.

Embodiment Hereinafter, a line monitoring device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a simplified tree-like transmission network in order to explain the principle of a line monitoring device according to a first embodiment of the present invention.

In Figure 1, 25 is the navel end, 30-3
Reference numeral 3 indicates a main line transmission system, and 40 to 49 indicate branch line transmission systems, which will be simply referred to as techniques hereinafter.

71 to 75 are branch points of the transmission path and are called nodes. 50-58
is a tap-off with an internal fault detector. In addition,
There are relay amplifiers on the branches, tap-offs and relay amplifiers at the nodes, and there are transmission lines and terminal equipment at the end of the tap-off with a fault detector, but these are omitted.

The operation of the line monitoring device configured as described above will be explained below with reference to FIGS. 1 to 5.

FIG. 2 shows a correspondence table between the multiple branches of the transmission path and the tap-offs having fault detectors connected under each branch of the transmission path in the transmission network of FIG. 1.

For example, tap off 54 has 30 techniques. Technique 31. Technique 32,
It can be seen that the signal is transmitted through the route of technique 47.

Now suppose that a failure occurs somewhere along the transmission path.

In other words, if a failure occurs somewhere among branches 30 to 49 (if a failure occurs in nodes 71 to 75, consider including it in any branch connected to that node), which Consider whether a fault is detected at tap-off. for example,
It can be seen from FIG. 2 that when a failure occurs in the technique 32, the failure is detected in the tap-offs 54 to 57 connected below the technique 32.

In this way, FIG. 3 shows the correspondence between the technique in which a failure occurred and the response of the failure detector for each tap-off.

In Figure 3, O is a state where no fault is detected, ×
indicates that a fault has been detected. In this way, by checking the response of the tap-off fault detector, it is possible to know which branch has failed. In addition,
In this example, the number of tap-off responses is 29, or 512, and even excluding the 15 shown in FIG. 3, there are 497 possible tap-off responses. These 497 cases can be broadly divided into cases in which failures occur in two or more branches at the same time, and cases in which failures cannot ideally occur. The probability of the former occurring is small, but
Most multiple disorders can be recognized using similar techniques. On the other hand, if a response belonging to the latter occurs, the monitoring terminal
This is a failure in the line monitoring device itself, such as a fault detector, and this can be used to discover failures in the line monitoring device itself.

FIGS. 4 and 5 show the tap-off and head-end circuit configurations of the line monitoring device in the first embodiment based on the above principle.

In FIG. 4, l is an input terminal, 27 is a fault detector, 1
0 is a transmission modulation circuit, 29 is an upper and lower signal separation filter, 3 is a directional coupler, 4 is a 5-way divider, 7 is an output terminal, 76 to 7
Reference numeral 9 denotes a branch output terminal, which constitutes the tap-off 5.

The failure detector 27 detects an abnormality in the downlink signal.

Various items can be considered as specific detection items, such as distortion, S/N, and oscillation, which are easy and effective to monitor at the terminal. Fault detector 27
When a fault is detected in the transmission modulation circuit IO, a fault detection signal is generated in the transmission modulation circuit IO so that the tap-off that detected the fault can be recognized and the details of the fault can be understood by the monitoring terminal, and this signal is sent to the monitoring terminal as an upstream transmission signal. transmitted. For example, the fault detection signal may be given a different carrier frequency for each tap-off, and the output, frequency, or phase may be changed depending on the presence or absence of a fault, or it may be modulated with a digital signal if there are many detection items. .

On the other hand, in FIG. 5, 13 is a head end output terminal;
14 is an upper and lower signal separation filter, 16 is a branching filter, 17 is a receiving and demodulating circuit, 20 is a control circuit, 26 is a storage device, 21 is a printing device, 22 is a display device, and 23 is a keyboard controller and above, which constitutes a monitoring terminal 24. has been done. Reference numeral 18 denotes a transmitting/receiving device, and the monitoring terminal 24 and the transmitting/receiving device 18 constitute a head end 25 . The fault detection signal is sent to the reception demodulation circuit 17 via the upper and lower signal separation filter 14 and the duplexer 16.
It is restored and enters the control circuit 20. The storage device 26 stores a correspondence table between each branch of the transmission path and the terminal device having a fault detector connected under each branch thereof, as shown in FIG. 2 or 3. , the control circuit 20 uses this correspondence table to determine the technique in which the failure has occurred.

Furthermore, the storage device may also store a correspondence table between each school and the relay amplifiers on its branches, so as to identify the relay amplifier in which a failure has occurred. These results are displayed on the display device 22.
, are displayed on the printing device 26. These displays may be performed interactively using the keyboard 23, or may be unilaterally output and displayed when a failure occurs.

As described above, according to this embodiment, a fault detector for detecting an abnormality in a downlink transmission signal and a transmission modulation circuit for sending out a fault detection signal are provided in tap-off mode, and a receiving demodulator for demodulating this fault detection signal is installed in the monitoring terminal. A storage means that stores a correspondence table between the circuit and each tap-off connected under each branch and each branch thereof, and when a failure detection signal is received from the tap-off, this correspondence table is used to determine which transmission path branch. By providing a control circuit that determines whether a fault has occurred in a relay amplifier, it is possible to accurately detect the occurrence of a fault and identify the faulty device or relay amplifier. , since the same effect can be obtained with fewer fault detectors, the system can be realized at low cost.

A second embodiment of the present invention will be described below with reference to the drawings.

6 and 7 are circuit configuration diagrams of a terminal device and a head end of a line monitoring device showing a second embodiment of the present invention.

In FIG. 6, 1 is an input terminal, 27 is a fault detector, 1
0 is a transmission modulation circuit, 29 is an upper and lower signal separation filter, 3 is a directional coupler, 4 is a 5-way divider, 7 is an output terminal, 76 to 7
Reference numeral 9 denotes a branch output terminal, which is similar to the configuration shown in FIG. 4. Reference numeral 9 denotes a reception demodulation circuit, which differs from the configuration shown in FIG. This is the point. Note that the tap-off 5 is configured as described above.

On the other hand, in FIG. 7, 13 is a head end output terminal;
14 is an upper and lower signal separation filter, 16 is a branching filter, 17 is a reception demodulation circuit, 20 is a control circuit, 26 is a storage device, 21 is a printing device, 22 is a display device, and 23 is a keyboard. The configuration is similar. The difference from the configuration shown in FIG. 5 is that a transmission modulation circuit 19 and a multiplexer 15 are provided.

The monitoring terminal 24 is configured as described above, and the head end 25 is further configured with the transmitting/receiving device 18.

The operation of the line monitoring device configured as described above will be explained below. The operation for identifying a faulty branch or relay amplifier is exactly the same as in the first embodiment. The difference from the first embodiment is that the failure detection signal is transmitted not in one direction, but in both directions, while exchanging commands. The control circuit 20 of the monitoring terminal 24 includes a transmission modulation circuit 19. A downlink command is sent using the multiplexer 15.

In response to this, the control circuit 2B of the tap-off 5 decodes the downlink command using the reception demodulation circuit 9, and in response, sends out an uplink command containing information from the fault detector 27 using the transmission modulation circuit 10. do. And monitoring terminal 2
The control circuit 20 of No. 4 is a branching filter 16. The reception demodulation circuit 17 is used to decode the upstream command and obtain information as to whether or not a fault has been detected at each tap-off. The communication procedure between the monitoring terminal 24 and the tap-off 5 may be a polling method that always calls each tap-off in turn, or a condensation method in which the terminal device sends a signal to the tap-off when a failure occurs and then starts communication. There may be one, or there may be a combination of both.

As described above, the output of the fault detector 27 of the tap-off 5 is input to the transmission modulation circuits 1 and 0 via the control circuit 28,
By providing the transmission modulation circuit 19 and the multiplexer 15 in the monitoring terminal 24, it has higher functionality such as increasing the number of failure detection items, and has more flexibility in system expansion, such as adding terminal devices with failure detectors. You can build a system with

Note that in both the first and second embodiments, the fault detector 27 is not provided for all tap-offs, but the fault detector 27 is provided only for tap-offs located at positions where the fault detection effect is large.
7 may be provided. For example, since most faults occur at relay amplifiers, if there are multiple tap-offs further downstream from the most distal relay amplifier in the transmission path, you only need to install a fault detector at one of these tap-offs. , the same fault detection ability can be obtained. By doing so, the system can be realized at a lower cost.

Effects of the Invention As described above, the present invention provides a tap-off having a fault detector for detecting an abnormality in a downstream transmission signal at the end of each branched transmission path of a transmission system, and a fault detection signal from each of these tap-offs. A means for concentrating transmission on a monitoring terminal, a storage means for storing a correspondence table of each school of each transmission path and each of these tap-offs connected under each in the monitoring terminal, and a failure detection signal from the tap-off is received. By providing a means to use this correspondence table to determine in which transmission route a fault has occurred, a line monitoring device can accurately detect the occurrence of a fault and identify the faulty link or relay amplifier. can be realized at low cost.

[Brief explanation of drawings]

FIG. 1 is a simplified diagram of a dendritic transmission network for explaining the principle of the line monitoring device in the first embodiment of the present invention, and FIG. 2 shows the multiple branches of the transmission path of the transmission network in FIG. Fig. 3 is a diagram showing the correspondence between the technique in which a fault occurs and the response of the fault detector of each tap-off. , FIG. 5 is a configuration diagram of the tap-off and head-end circuits of the line monitoring device in the first embodiment of the present invention, and FIG.
FIG. 7 is a configuration diagram of the tap-off and head-end circuits of the line monitoring device in the second embodiment of the present invention, FIG. 8 is a configuration diagram showing an example of a CATV transmission network, and FIGS. 9 and 10 are FIG. 3 is a circuit configuration diagram of a relay amplifier and a head end of a conventional line monitoring device, respectively. 1...Input terminal, 3...Directional coupler, 4...5 distributor, 7...Output terminal,
28, 2.0... Control circuit, 9, 17...
...Reception demodulation circuit, 13... Head end output terminal, 14.29... Upper and lower signal separation filter,
15...Multiplexer, 16...Demultiplexer, 1
8... Transmission/reception device, 10.19... Transmission modulation circuit, 21... Printing device, 22...
...Display device, 3゜23...Keyboard, 24
...Monitoring terminal, 25...Harm detector, 30-3
3...techniques (mainline transmission system), 40-49...
... Techniques (branch line transmission system), 50-58 and 5...
...Tap-off, 71-75, old...node (transmission path branch point), 76-79...branch point output terminal. Name of agent: Patent attorney Toshio Nakao Haka 1 person 30-33
-One technique (main line transmission system) 40~49 -One technique (branch line, stingy! delivery system) 71~75
- Medical treatment (transmission path branching point) Fig. 2 Fig. 7 25 Head end

Claims (6)

[Claims] (1) A wired transmission system that extends in a dendritic manner from the head end, with a tap-off at the end of each branched transmission path of the transmission system having a fault detector for detecting abnormalities in the downlink transmission signal, and from each of the tap-offs. means for transmitting and concentrating failure detection signals of the above to a monitoring terminal; and a storage means in the monitoring terminal that stores a correspondence table between each branch of each transmission path and the tap-off connected below each branch; A line monitoring device comprising means for determining in which branch of a transmission path a fault has occurred, using the correspondence table when fault detection signals are received from a plurality of the tap-offs. (2) The line monitoring device according to claim 1, wherein the transmission system is a CATV transmission system. (3) The correspondence table shows the correspondence between each branch of the transmission path and the interrupting amplifier in that branch, and it is possible to know which interrupting amplifier has a failure. The line monitoring device according to item 1 or 2. (4) The line monitoring device according to claim 1, 2 or 3, wherein the means for transmitting the failure detection signal to the monitoring terminal uses uplink transmission of the transmission system. (5) The tap-off and monitoring terminals having a fault detector have bidirectional communication means and transmit fault detection signals by mutually exchanging commands. Line monitoring device. (6) Any one of claims 1 to 5, characterized in that each branched transmission path has one tap-off having a fault detector further downstream from the discontinuing amplifier at the end of each branched transmission path. A line monitoring device described in .