JPS61194988A - Operation monitoring system for catv repeater amplifier - Google Patents

Abstract

PURPOSE:To detect automatically and prescribedly the failed repeater amplifier by receiving the operation detection signal by the receiver at the subscriber terminal from which a received abnormal operation signal is sent through a transmitter and the public line to the center. CONSTITUTION:A failed one-way repeater amplifier 6 causes the output level to be lower or higher than the specified level. This change in level is output as the output level detection signal from the level comparator 18. With this output level detection signal, CPU 26 detects the failure of the repeater amplifier 6. Upon judgement as failure of the one-way repeater amplifier 6, the CPU 26 allows the transmitter 27 to automatically call as well as adds an address of the one-way repeater amplifier to the abnormal operation signal, and delivers this abnormal operation signal to the transmitter 27. The transmitter 27 connected with the public line 31 sends this abnormal operation signal through the public line 31 to the center 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a method for monitoring the operation of a CATV repeater amplifier and detecting abnormalities therein, and particularly relates to a method for monitoring the operation of a CATV repeater amplifier and detecting an abnormality thereof, particularly in a CATV system equipped with a unidirectional repeater amplifier. This invention relates to a method for monitoring the operation of.

(Technical background of the invention and its problems) Recently, CATV systems equipped with a plurality of bidirectional repeater amplifiers have been provided, and this allows subscriber side terminals (image receiving m)
It allows television signals to be sent to the center via the downlink, and various information from subscriber terminals to the center via the uplink. That is, for example, as shown in FIG.
(VHF, etc.) ■Special frequency bands 2 and 3 are provided for downlink and uplink, and frequency band 2 for downlink
The operation control signal and the monitoring signal for the bidirectional relay amplifier are assigned to , and the uplink frequency band 3 is assigned signals containing various information. Therefore, one of the two-way relay amplifiers may fail, making it impossible to send the television blind signal to the subsequent subscriber side, or one of the two-way amplifiers may cause oscillation or the like, causing interference with the television signal. When distortion such as modulation occurs, simply output an abnormality detection signal from the faulty bidirectional amplifier to the uplink, and the center side will be able to determine which bidirectional relay amplifier has a fault. can be known.

By the way, most of the existing CATV systems have a configuration using a unidirectional repeater amplifier, so as mentioned above, the i! l! II cannot. For this reason, CAT with multiple unidirectional relay amplifiers
In the V system, failures in unidirectional repeater amplifiers could not be detected unless there was a complaint from a subscriber or on-site maintenance work by a worker. and,
During maintenance work, it is not possible to identify which relay amplifier is malfunctioning unless each of the multiple unidirectional relay amplifiers installed on the transmission line is inspected.
The drawback is that maintenance work requires a lot of time and effort.

(Object of the Invention) The object of the present invention is to
An object of the present invention is to provide a method for monitoring the operation of a CATV repeater amplifier that can automatically and specifically detect failures in the repeater amplifier in a TV system.

(Summary of the Invention) The present invention superimposes an address signal indicating one of the unidirectional relay amplifiers on a pilot signal, and also allows each unidirectional relay amplifier to detect its own operation and send an operation detection signal to the television signal. A motion detection means is provided that outputs a narrow band frequency within a frequency band to which a specific vacant channel is assigned, and the motion detection signal is detected from any one of the unidirectional repeating amplifiers that is malfunctioning due to input of the pilot signal. This motion detection signal is received by a receiver installed in the subscriber terminal, and based on this motion detection signal, it is determined whether or not there is an abnormal operation. The system is characterized in that an abnormal operation signal is output via a public line via an automatic transmitter or the like.

(Embodiments of the Invention) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the overall configuration of a CATV system according to the present invention, and 4 in the figure indicates the center. This center 4 includes a coaxial cable 5 as a transmission line and a branch transmission line.
5' is connected.

These coaxial cables 5, 5' are laid overhead, and a plurality of unidirectional repeater amplifiers 6 are arranged respectively.

Each unidirectional relay amplifier 6 includes an amplification section 7, as shown in FIG. The input side and output side of this amplifying section 7 are connected to the coaxial cable 5 or 5' via an input terminal 8 and an output terminal 9. A directional coupler 1 is provided on the output side of the amplifier section 7.
A pilot signal selection filter 11 is connected to this directional coupler lO for extracting only the pi c1-/to signal. An amplifier 12 for amplifying the selected pilot signal is connected to the filter 11, and an amplifier section 7 is connected to the output side of the amplifier 12 via a rectifier 13.
An AGC circuit 14 for controlling the gain of is connected. Further, an FSK (frequency shift keying) detector 15 is connected to the output side of the amplifier 12, and a decoder 16 is connected to the output side of the FSK detector 15. A control section 17 is further connected to the output side of this decoder 16.
A level comparator 18 controlled by a data acquisition signal is connected to 7. A reference voltage is applied to the level comparator 18 , which compares the reference voltage with the output level from the amplifier section 7 and outputs an operation detection signal to the control section 17 . An FSX modulator 19 is connected to the output side of the control section 17. This FSK modulator 19 performs FSKf modulation of the pulsed motion detection signal output from the control section 17 using a narrow band carrier wave, which will be described later, and sends the modulated wave to the downstream coaxial cable 5 or 5' via the mixer 20. Output to.

As shown in FIG. 1, a receiver 21 as a subscriber terminal is connected to the coaxial cable 5 or 5', and a receiver 22 is further connected to the receiver 21. As shown in FIG. 3, this receiver 2 includes a filter 23, and this filter 23 has a characteristic of passing only FSX modulated waves.

An FSK detector 24 is connected to the filter 23 .

On the output side of this detector 24, there is a decoder 25 and a CPU 2.
6 are connected in this order. A transfer device 27 is connected to the output side of the CPU 26, and the output signal of the CPU 26 is transmitted to the first
As shown in the figure, the public line 31
The data is sent to the center 4.

Next, the operation monitoring system of the present invention will be explained together with the operations of each of the above devices.

That is, the center 4 outputs the television signal 28 and pilot signal 29 of each channel to the coaxial cable 5, as shown in FIG.

Therefore, the television signal 28 is amplified by the amplifying section 7 via the input terminal 8 of the unidirectional relay amplifier 6 in the previous stage,
The signal is sequentially sent from the output terminal 9 via the coaxial cables 5 and 5' to the unidirectional relay amplifier 6 on the downstream side, and is received by the receiver 21 on each subscriber side. On the other hand, after the pilot signal 29 is amplified by the amplifier section 7, a part thereof is sent to the directional coupler 10 together with the television signal 28, and is selected by the filter 11. And amplifier 12
The AG
The signal is input to the C circuit 14 as a gain control signal. Therefore,
The gain of the amplifier section 7 is controlled by this AGC circuit 14.

Now, in the operation monitoring system of the present invention, an address signal indicating one of the unidirectional relay amplifiers 6 is FSK-modulated in a narrow band and superimposed on the pilot signal 29 at the center 4 side. Therefore, the biloft signal 29 is sent to the unidirectional relay amplifier 6.
When the pilot signal 29 is input, the gain of the amplifier section 7 is controlled as described above, and at the same time, the pilot signal 29 is input to the FSX detector 15.
Since the FSK modulated wave indicating the address superimposed on the pilot signal 29 is detected (demodulated) by the FSK detector 15, the address is decoded by the decoder 16.

The control unit 17 determines whether this decoded address is its own address or not. If the control unit 17 determines that this address is not the address of another unidirectional relay amplifier 6, the control unit 17 controls the operation of the level comparator 18. No signal is output, and therefore, a signal detected from the level comparator 18 that detects the output level of the television signal amplified by the amplifying section 7 is not inputted to the control section 17.

On the other hand, if the control section 17 determines that the decoded address is an address indicating its own unidirectional relay amplifier 6, the control section 17 outputs an operation control signal to the level comparator 18, and the control section 17 outputs an operation control signal to the level comparator 18. The control unit 17 takes in the output level detection signal of the amplifier unit 7 detected by the output level detection signal, and after adding an address indicating its own relay amplifier 6 to this output level detection signal, the control unit 17 performs FSK modulation on the detection signal. output to the device 19. The FSX modulator 19 is as shown in FIG.

The address and output level detection signal 30 is used to perform FSK modulation on a carrier wave having a narrow band frequency within the frequency band to which a specific vacant channel of the television signal 28 is assigned, and the FSK modulated wave is sent to the mixer 20 to amplify the television. output to be superimposed on the John signal 28. Therefore, this FSK
The modulated wave is sent to the receiver 21 along with the television signal 28 via the coaxial cable 5 (5') in the downward direction.

In this way, after sending the FSK modulated wave and the television signal 28 to the receiver 21, these signals are sent to the receiver 22.
send to In the receiver 22, as shown in FIG.
The FSK modulated wave is input to the FSK detector 24 and detected (demodulated), so the output level detection signal and the added address signal are decoded by the decoder 25 and input to the CPU 26. CPU26 is 4
Based on the output level detection signal, it is determined whether the unidirectional relay amplifier 6 corresponding to the address is operating normally.

That is, when a failure or oscillation occurs in the unidirectional relay amplifier 6, the output level becomes larger or smaller than a predetermined level, and the level change is outputted from the level comparator 18 as an output level detection signal. , the CPU 26 can know from this output level detection signal that a failure or the like has occurred in the relay amplifier 6.

When the CPU 26 determines that a failure or the like has occurred in the unidirectional relay amplifier 6, the CPU 26 causes the transfer device 27 to automatically make a call, adds the address of the unidirectional relay amplifier 6 to the abnormal operation signal, and then detects this abnormal operation. The signal is output to the transfer device 27. Therefore.

Since the transmitter 27 is connected to the public line 31, this abnormal operation signal is sent to the center 4 along with the address signal via the public line 31. Therefore, by providing a terminal such as a facsimile at the center 4, It is possible to automatically and instantly know whether the unidirectional relay amplifier 6 is operating abnormally.

In the above embodiment, the control unit 1 of each unidirectional relay amplifier 6
7, an alarm signal with an address added thereto may be output, and this alarm signal may cause the receiver 22 to automatically make a call and send an abnormal operation signal to the center 4 via the public line 31.

In the above embodiment, the address signal is FSX modulated and superimposed on the pilot signal, but it goes without saying that the address signal may be superimposed using FM modulation, PSK modulation, or the like. In this case, a receiver capable of receiving each modulated wave may be used.

(Effects of the Invention) According to the present invention, an address signal indicating each unidirectional relay amplifier is superimposed on a pilot signal, and operation detection is performed in which each unidirectional relay amplifier detects its own operation and outputs an operation detection signal. This motion detection signal is received by a receiver installed in the subscriber terminal, and if an abnormality occurs in the corresponding unidirectional relay amplifier, the receiver transmits it to the public via a transmitter, etc. By sending abnormal operation signals to the center side via the line, C
Even in an ATV system, the center side can automatically and instantaneously know malfunctions in the operation of each unidirectional repeater amplifier.

In addition, since the motion detection signal is modulated using the narrowband frequency of a specific vacant channel, there is no need to provide a separate line outside the frequency band for television signals, and since the motion detection signal is modulated using a narrowband frequency, each individual There is no problem with the AGC operation of the directional repeater amplifier, and furthermore, it can be applied to a CATV system including a unidirectional repeater amplifier that does not require control or the like in the system.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an example in which the operation monitoring method according to the present invention is applied to a CATV system, FIG. 2 is a circuit configuration diagram of a unidirectional relay amplifier according to the present invention, and FIG. 3 is a reception diagram according to the present invention. 4 is a characteristic diagram showing the relationship between the frequency and gain of each signal according to the present invention, and FIG. 5 is a bidirectional CA circuit diagram.
FIG. 2 is a characteristic diagram showing the relationship between the frequency and gain of each signal in the TV system. 4-----One center, 5.5'---One coaxial cable, 6-------Unidirectional relay amplifier, 7-------
-----Amplification unit, 10------Unidirectional coupler, 11.23---Filter, 15.24---FSK detector, 16.25------ -Decoder, 17-------Control unit 17. 18---1---Level comparator, 19---FSK modulator, 20---1---Mixer. 21-------1 receiver, 22------1 receiver, 26---------CPU, 27---------transmitter. 28------- Television signal, 29--1-
----- Pilot 7 signal. 31--------Public line. (1 other person) Fig. 1 4 ------- Yanter 5.5' ---- Single coaxial cable 6 ------- Unidirectional center repair amplifier 21 ---- --One receiver 22=-One to ---Receiver 27---Transfer 31---One public line

Claims (1)

[Claims] A television signal and a pilot signal are sent from a center to a transmission path, and the pilot signals are used to control the gains of a plurality of unidirectional relay amplifiers arranged on the transmission path, and the television signals are transmitted by the plurality of unidirectional relay amplifiers. In a CATV system in which the pilot signal is sequentially amplified to compensate for attenuation in the transmission path and sent to a subscriber terminal, an address signal indicating one of the unidirectional relay amplifiers is superimposed on the pilot signal, and to the relay amplifier,
The pilot is provided with a motion detection means for detecting its own motion based on the address signal and outputting a motion detection signal having a narrow band frequency within a frequency band assigned to a specific vacant channel of the television signal. When a signal is input, a motion detection signal is output from the unidirectional relay amplifier corresponding to the address to the transmission line, and the motion detection signal is received by a receiver provided in the subscriber side terminal, and the receiver detects the motion. An operation monitoring system for a CATV repeater amplifier, characterized in that an abnormal operation is detected based on a detection signal, and an abnormal operation signal is output to the center through a public line.