JPS61156928A - Automatic switch system of communication line - Google Patents

Abstract

PURPOSE:To detect easily the disconnection of a line by transmitting periodically a test signal to an active and spare communication line from a sending end and supervising a signal and the test signal from the sending end at the receiving end of the active and spare communication line to switch automatically a faulty line. CONSTITUTION:A transmission station is provided with a test signal generating circuit 9 generating a test signal, a switch circuit 11 transmitting selectively the signal of a transmitter and the test signal of the circuit 9 to the active and spare communication lines 3, 4 via a branch circuit 2, and a timer 10 switching periodically the switch circuit 11. On the other hand, the reception station is provided with supervisory circuits 12, 13 supervising the signal and the test signal transmitted to the lines 3, 4 and using the switch circuit 7 to switch the communication line to the other when the signal is not detected or an error is found out within the setting time of timers 14, 15. Thus, the test signal is transmitted to the active and spare communication lines periodically and the reception end supervises the said test signal for line switching, then even when the transmitter transmits no signal, the disconnected line of the active and spare lines is detected to improve the reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic switching system for a communication line consisting of one working communication line and one protection communication line.

[Conventional technology]

Conventionally, switching from a working communication line to a backup communication line in a communication line employing a polling method or the like has been carried out by detecting errors in the received signal in a receiver.

FIG. 2 is a block diagram showing such a conventional communication line automatic switching system.

The transmitter 1 sends a signal including an address, a command, etc. to the receiver 8 with which communication is required. This signal is the branch circuit 2
The data is sent out onto the working communication line 3 and the backup communication line 4. In the receiving station, error detection is performed in monitoring circuits 5 and 6 connected to the working line 3 and backup communication line 4, respectively, and when a failure is detected, switching is performed by the switching circuit 7.

[Problem that the invention seeks to solve]

However, in such conventional switching methods, the detection value of the monitoring circuit is the same when no signal is being sent from the transmitting station and when the line is disconnected; Unable to detect line disconnection.

[Means for solving problems]

The present invention periodically transmits a test signal from the transmitting end onto the working and backup communication lines, and monitors the signal from the transmitting end and the test signal at the receiving end of the working and backup communication lines. It is characterized by automatic line switching.

Therefore, signals (signals from the transmitting station and test signals) are always being sent to the communication line, and line breakage can be easily detected even when no signals are being sent from the transmitting side.

〔Example〕

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an automatic line switching system according to the present invention.

The transmitting station includes a test signal generation circuit 9 that generates a test signal;
A switching circuit 11 for selectively sending the transmitter signal and the test signal from the test signal generation circuit 9 to the working and backup communication lines 3.4 via the branch circuit 2, and for periodically switching the switching circuit 11. A timer lO is provided.

On the other hand, the receiving station monitors the signals and test signals transmitted on the working and backup communication lines 3.4, and sets the timer (working) 14 and timer (protection) 15 respectively (timer lO on the transmitting side). If these signals cannot be detected or if an error is detected, the switching circuit 7 switches the communication line to the other party. ) 13 are provided.

In this way, a test signal is periodically sent out on the working communication line 3 and the backup communication line 4, and the monitoring circuit 12.13
Since this is monitored by , it is possible to detect a line disconnection failure even when no signal is being sent from the transmitting side.

〔Effect of the invention〕

As explained above, in the present invention, a test signal is periodically sent to the working and backup communication lines, the main test signal is monitored at the receiving end, and the line is switched from this K, so that the transmitter transmits the signal. Even when no transmission is being performed, disconnection of the working and protection lines can be detected, which has the effect of improving reliability.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an automatic communication line switching system according to the present invention, and FIG. 2 is a block diagram of a conventional example. l: Transmitter 2: Branch circuit 3: Working communication line 4: Backup communication line 7.11: Switching circuit 8: Receiver 9: Test signal generation circuit 10: Timer 12:
Monitoring circuit (current use) 13: Monitoring circuit (spare use) 14: Timer (current use) 15: Timer (spare use).

Claims (1)

[Claims] In an automatic communication line switching system that consists of one working communication line and one protection communication line, a test signal is periodically sent from the transmitting end to the working and protection communication lines, and the An automatic communication line switching system characterized in that a faulty communication line is automatically switched by monitoring a signal from a transmitting end and the test signal at a receiving end.