JPH067334U - Transmission line switching device for CATV - Google Patents

Abstract

(57) [Abstract] [Purpose] With a simple circuit configuration, it is possible to connect as many backup transmission lines as necessary. [Configuration] Input terminals 3 and 4 for connecting an input side main transmission line 1 and a backup transmission line 2 and output terminals 5 and 6 for connecting an output side main transmission line 1 and a backup transmission line 2 are provided. The output terminals 5 and 6 are respectively provided with switchers 7 and 8 which can be switchably connected to the input terminals 3 and 4. The input terminals 3 and 4 detect the level of the input signal thereof and switch the switches 7 and 8 respectively. The control circuits 9 and 10 for switching and controlling are provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention is intended to enable the downlink signal flowing in the backup transmission line to be transmitted to the subscriber side transmission line instead of the main transmission line when the downlink signal of the main transmission line stops due to some cause. The present invention relates to a transmission line switching device for CATV.

[0002]

[Prior art]

 Conventionally, in a CATV system, when a transmission line for transmitting a head-end downlink signal to a subscriber fails and a failure such as a signal stoppage occurs, this occurs until the transmission line is restored. Some have a backup transmission line for transmitting downlink signals instead of the above. In such a CATV system, as shown in FIG. 3, the downlink signal from the headend is output in parallel with the main transmission line A and the backup transmission line B, and is connected in the middle of both transmission lines A and B. The transmission line switch C is connected to the main transmission line A when it is normal, and automatically switches to the backup transmission line B when it is abnormal, and the downlink signal of the backup transmission line B is transmitted to the transmission line D after that. It is supposed to be done.

Specifically, as shown in FIG. 3, the transmission line switch C is connected to the input terminals E and F for connecting the main transmission line A and the standby transmission line B and the transmission line D on the terminal side. There is an output terminal G. An input terminal E connecting the main transmission line A is provided with a detection circuit H and a comparison circuit I for detecting and checking the level of the input signal, and the comparison circuit I is used as an input signal. When it is determined that there is no abnormality, a signal is sent to the drive unit J and the switch K is operated to set the downlink signal of the main transmission line A to the transmission line D on the terminal side. Further, when an abnormality is detected in the level of the downlink signal from the main transmission line A, the comparison circuit I sends a signal to the driving unit J, and the driving unit J receiving this signal switches the switching unit K. It switches and outputs the downlink signal of the backup transmission line B to the transmission line D on the terminal side.

[0004]

However, since the transmission line switch C of FIG. 3 has only one output terminal G, it is not possible to provide a backup transmission line to the transmission line D after that, and as a result, However, when a failure such as a signal stoppage occurs in the transmission path D after the transmission path switch C, there is a problem that the transmission to the participants in the area is stopped.

An object of the present invention is to provide a CATV transmission line switching device which has a simple circuit configuration and can be connected to as many spare transmission lines as necessary.

[0006]

[Means for Solving the Problems]

 As shown in FIG. 1, the CATV transmission line switching device of the present invention has input terminals 3 and 4 for connecting an input side main transmission line 1 and a backup transmission line 2, and an output side main transmission line 1 and a backup transmission line. The output terminals 5 and 6 for connecting the path 2 are provided, and the output terminals 5 and 6 are provided with switchers 7 and 8 that can be switchably connected to the input terminals 3 and 4, respectively. Control circuits 9 and 10 for detecting the level of the input signal and controlling the switching of the switching devices 7 and 8 are provided.

[0007]

[Action]

 In the CATV transmission line switching device of the present invention, when normal signals are input to the input terminals 3 and 4, respectively, the control circuits 9 and 10 that detect the normal signals control the switching devices 7 and 8. Since the signals of the input terminals 3 and 4 are transmitted to the output terminals 5 and 6 as they are, even if a plurality of transmission line switching devices 11 are installed as shown in FIG. Each signal is transmitted to 2. Further, even if one of the input terminals 3 and 4 stops, the control circuits 9 and 10 that detect it control the switching devices 7 and 8 to output the normal signal to the two output terminals 5. , 6 is transmitted separately, so in the case of FIG. 2, the main transmission line 1 and the backup transmission line 2 connected to the output terminals 5 and 6 of the transmission line switching device 11 ahead of them are retransmitted to the signal again. Is transmitted.

[0008]

【Example】

 In FIG. 2 showing an embodiment of a transmission path switching device for CATV of the present invention, 20 is a head end of CA TV, 1 and 2 are main transmission paths and standby transmission paths for transmitting signals output from head end 20. Of these, the backup transmission line 2 is used temporarily when the main transmission line 1 goes down until it is restored. A transmission line switching device 11 of the present invention is attached in the middle of the main transmission line 1 and the backup transmission line 2. A relay transmission device 21 such as a main line amplifier is provided in the middle of the main transmission line 1 and the backup transmission line 2.

The transmission line switch 11 connects the input terminals 3 and 4 for connecting the main transmission line 1 and the standby transmission line 2 on the input side to the main transmission line 1 and the standby transmission line 2 on the terminal side. And output terminals 5 and 6 for The wiring of each of the input terminals 3 and 4 is divided into two by the distributor 22. The four wirings of the input terminals 3 and 4 and the two wirings of the output terminals 5 and 6 are 6-contact switching devices. 7 and 8 are connected. The switches 7 and 8 are composed of an electromagnetic relay, a matrix circuit, etc., and are capable of automatically electrically connecting arbitrary contacts with each other by an electric signal from the outside.

A branching device 23 for extracting a part of the signal is attached in the middle of the wiring of the input terminals 3 and 4, and the branching output is output to the control circuits 9 and 10. There is. Both control circuits 9 and 10 are the same, and the detector 24 for detecting the input signal and whether the signal at the input terminal 3 (or 4) is normal by comparing the detected voltage with the reference voltage. And a drive unit 26 that causes the switches 7 and 8 to switch the contacts based on the control signal of the comparison circuit 25.

Here, a specific switching pattern of the switches 7, 8 by the control circuits 9, 10 will be described. First, when normal signals are sent to both the input terminals 3 and 4, the contact points of the switching devices 7 and 8 and the contact points are indicated by solid lines in the figure by the control circuits 9 and 10. After being connected, the main transmission line 1 and the backup transmission line 2 on the head end side are directly connected to the main transmission line 1 and the backup transmission line 2 on the subscriber side. Next, when the signal of the input terminal 3 stops and a normal signal is sent to the input terminal 4, the control circuits 9 and 10 connect the contacts of the switching devices 7 and 8 and the contacts. Then, the signal of the backup transmission line 2 is distributed by the distributor 22 and output to the main transmission line 1 and the backup transmission line 2 on the subscriber side. Further, when a normal signal is sent only to the input terminal 3, the control circuits 9 and 10 connect the contacts of the switching devices 7 and 8 to each other, and the signal of the main transmission line 1 is distributed to the distributor. It is distributed by 22 and is output to the main transmission line 1 and the standby transmission line 2 on the subscriber side.

[0012]

[Effect of device]

 In the CATV transmission line switching device of the present invention, it is possible to configure a redundant system in which a plurality of transmission line switching devices 11 as shown in FIG. The backup function consisting of the main transmission line 1 and the backup transmission line 2 works independently in the network, and unless both the main transmission line 1 and the backup transmission line 2 go down in the same section, the signal stop The system reliability is greatly increased because it does not cause waves.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a transmission line switching device for CATV of the present invention.

FIG. 2 is a schematic diagram showing a usage state of the CATV transmission path switching device of FIG.

FIG. 3 is a block diagram showing an example of a conventional CATV transmission path switch.

[Explanation of symbols]

 1 main transmission line 2 backup transmission line 3, 4 input terminal 5, 6 output terminal 7, 8 switching device 9, 10 control circuit

Claims (1)

[Scope of utility model registration request] 1. An input terminal 3, 4 for connecting an input-side main transmission line 1 and a backup transmission line 2, and output terminals 5, 6 for connecting an output-side main transmission line 1 and a backup transmission line 2. The output terminals 5 and 6 are provided with switchers 7 and 8 which can be switchably connected to the input terminals 3 and 4, respectively, and the input terminal 3 and 4 detect the level of the input signal to detect the input signal level. , 8 is provided with control circuits 9 and 10 for switching control.