JPS6333338B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to a double-line switching system for a time-division multiplex communication system in which opposing time-division multiplex communication devices are connected through working and backup lines, and particularly relates to This invention relates to a double line switching system that automatically switches lines in the event of a failure.

(b) Prior Art and Problems FIG. 1 is a block diagram showing the circuit configuration of a conventional time division multiplex communication system.

In the figure, 1 and 2 are time division multiplex communication devices, 3 and 4 are multiplexing/modem units, 5 is a working line, 6 is a protection line, and SW1 to SW4 are switches.

In FIG. 1, normally a time division multiplex communication device 1
The transmission is multiplexed by the multiplexing/modem unit 3, and the analog signal converted from digital to analog is transmitted via the switch SW1 and the working line 5, and the time division multiplex communication device 2 switches the received signal. The signal is received by the multiplexing/modem unit 4 via the SW 3, converted into analog/digital data, and demultiplexed. The transmission from the time division multiplex communication device 2 is multiplexed by the multiplexing/modem unit 4, and the analog signal converted from digital to analog is transmitted via the switch SW 4 and the working line 5, and the received signal is sent to the time division multiplex communication device 1. Switch SW2
received by the multiplexing/modem unit 3 via
Analog-to-digital conversion and demultiplexing.

For example, if a failure occurs on the working line 5, the receiving side of the multiplexing/modem unit 3 will lose synchronization, and an ALM will occur immediately within 2 seconds.
As a result, on the time division multiplex communication device 1 side, the switches SW1 and SW2 are manually switched between the dotted lines.
On the time division multiplex communication device 2 side, the above operation causes the receiving side of the multiplexing/modem unit 4 to become out of synchronization. As a result, switches SW3 and SW4 are manually switched to the dotted line side. Through the above operation, the working line 5 is switched to the protection line 6 and communication continues.

However, this method has the disadvantage that switching is done manually, which takes time and effort.

(c) Object of the Invention In view of the above-mentioned conventional drawbacks, the object of the present invention is to provide a double line disconnection system that can automatically switch the line in the event of a line failure.

(d) Structure of the Invention In order to achieve the above object, the present invention provides a multiplexing/modem unit of a time division multiplex communication device equipped with a switch normally connected to the transmitting side of the working and protection lines. is transmitted via both working and backup transmission lines, and reception is performed from the working line via the working and protection line changeover switch, and when the working receiving line fails, the protection is switched to the protection line by the out-of-synchronization detection signal from the multiplexing/modem unit. The receiving line has a receiving switch switching circuit for switching the switching switch, and a time division multiplex communication device facing the above switch of the sending line, which has become a backup line due to the switching, detects a loss of synchronization and operates the switching switch of the receiving line. The present invention is characterized in that it has a transmission switch control circuit that allows a sufficient period of time to be interrupted, and automatically switches to a protection line in the event of a fault in the working line.

(e) Embodiment of the invention An embodiment of the invention will be described below with reference to the drawings. FIG. 2 is a block diagram showing the circuit configuration of a time division multiplex communication system according to an embodiment of the present invention.

Components in the figure that have the same functions as those in FIG. 1 are indicated by the same symbols. 1' and 2' are time division multiplex communication devices, 3' and 4' are multiplexing/modem units, 7 and 8 are transmitting switch control circuits, 9 and 10 are receiving switch control circuits,
SW2', SW3', SW5 to SW8 indicate switches.

Normally, the transmission from the time division multiplex communication device 1' is as follows:
The multiplexing/modem unit 3' transmits the data via the connected switches SW5, SW6, the working line 5 and the protection line 6, and the time division multiplex communication device 2' transmits the data via the working line 5. The signal sent from the time division multiplex communication device 2' is received by the multiplexing/modem unit 4' via the switch SW3', and the signal sent from the time division multiplexing communication device 2' is directly transmitted from the multiplexing/modem unit 4'. Switch SW7, SW
8. The signal is transmitted via the transmitting line of the working line 5 and the protection line 6, and in the time division multiplex communication device 1', the signal sent via the working line 6 is sent to the switch SW.
2', the multiplexing/modem unit 3' receives the data.

Now, for example, if a failure occurs on the B side of the working line 5, the multiplexing/modem unit 3' will detect an out-of-synchronization due to the above-mentioned failure, confirm that it is out of synchronization for about 2 seconds, and send an abnormal signal first. It is sent to the reception switch control circuit 9 and later to the transmission switch control circuit 7. As a result, the reception switch control circuit 9 switches the switch SW2' to the dotted line side. In addition, the transmitting switch control circuit 7 opens the switch SW5 of the working line 5, which has become a protection line, for T seconds, which is a sufficient time for the opposing time division multiplexer to detect the synchronization loss and operate the receiving line changeover switch. do. As a result, the multiplexing/modem unit 4' detects the loss of synchronization and sends the abnormal signal to the receiving switch control circuit 10 first.
Then, it is later sent to the transmission switch control circuit 8. This causes the reception switch control circuit 10 to
SW3' is switched to the dotted line side, and the signal transmitted from the protection line 6 side is received. At this time, there is no abnormality on the protection line 6' side, so synchronization can be established immediately. At this time, the transmission switch control circuit 8 controls the switch SW on the side of the working line 5, which has become a protection line.
7 is opened for T seconds, the multiplexing/modem unit 3' is in a receiving state from the C side of the protection line 6 and maintains the current state, so that communication is carried out through the protection line. In the above case, if switch SW2' is switched due to a failure on the C side of protection line 6, synchronization cannot be achieved, and if you want to prevent short-term (approximately 2 second intervals) repeated switching of switch SW2',
After switching, the line remains on the same line for T seconds and is not switched again. In this way, if there is a failure on the C side of the protection line 6 that causes a delay in synchronization due to noise or the like, reswitching can be prevented. Furthermore, if a spare reception line carrier disconnection detection circuit is added to the reception switch control circuits 9 and 10, and the switching is not performed when the reception line on the switching partner side is carrier disconnected, switching can be prevented, for example in the above case. If the C side of the protection line 6 is disconnected, the switch SW2' is not switched and repeated switching is not performed. Also, during loopback, the multiplexing/modem unit 3',
If the received signal is not received at 4', the multiplexing
Since the modem units 3' and 4' know this by themselves, by not sending alarm signals to the receiving switch control circuits 9 and 10, switching can be prevented from being executed during loopback.

Of course, the present invention can also be applied to a case where there is a working multiplexing/modem unit as a standby, and when the working multiplexing/modem unit fails, both transmission and reception lines are switched to the standby side.

(f) Effects of the Invention As explained in detail above, according to the present invention, in a time division multiplex communication system in which opposing time division multiplex communication devices are connected by working and backup lines, line switching is automatically performed in the event of a line failure. This has the effect of allowing line switching to be performed quickly and without much effort.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the circuit configuration of a conventional time division multiplex communication system, and FIG. 2 is a block diagram showing the circuit configuration of a time division multiplex communication system according to an embodiment of the present invention. In the figure, 1, 1', 2, 2' are time division multiplex communication devices,
3, 3', 4, 4' are multiplexing/modem units, 5
is a working line, 6 is a protection line, 7 and 8 are transmitting switch control circuits, 9 and 10 are receiving switch control circuits,
SW1 to SW8, SW2', and SW3' indicate switches.

Claims (1)

[Claims] 1. A time division multiplex communication system in which opposing time division multiplex communication devices are connected by working and protection lines, comprising a switch normally connected to the transmitting side of the working and protection lines, Transmission from the multiplexing/modem unit of the time division multiplex communication device is performed via both working and protection transmission lines, and reception is performed from the working line via the working and protection line switching switch, and when the working receiving line fails. , has a reception switch control circuit that switches the changeover switch to the backup reception line in response to an out-of-synchronization detection signal from the multiplexing/modem unit, and also switches the switch on the transmission side line that has become the protection line by the above switching when the opposite side is connected. The division multiplex communication device is characterized by having a transmission switch control circuit that detects synchronization loss and interrupts the receiving line for a sufficient period of time to operate the receiving side line changeover switch, and automatically switches to the protection line when the working line fails. Double line switching method. 2. In a time division multiplex communication system in which opposing time division multiplex communication equipment is connected by a working line and a protection line, a switch normally connected to the transmitting side of the working line and the protection line is provided, and the time division multiplex communication apparatus Transmission from the multiplexing/modem unit is performed via both working and protection transmission lines, and reception is performed from the working line via the working and protection line changeover switch, and when the working receiving line fails, the multiplexing/modem unit It has a reception switch control circuit that switches the switch to the backup reception line in response to an out-of-synchronization detection signal from the unit, and the opposing time division multiplex communication device synchronizes the switch on the transmission side line that has become the backup line by the above switching. A transmitting switch control circuit that detects a disconnection and disconnects the receiving line for a sufficient time to operate the receiving side line changeover switch, and means for preventing reswitching during the synchronization pull-in delay time due to noise etc. after the previous switching time; A double line, characterized in that the means for not performing switching during loopback and the reception switch control circuit include a carrier disconnection detection circuit for the receiving line, and the switching of the changeover switch is not performed when the receiving line on the switching partner side is carrier disconnected. Switching method.