JPH05235803A - Transmission line termination circuit - Google Patents

Abstract

PURPOSE:To improve the reliability and to reduce number of circuit components by not providing a changeover section for an active system and a standby system so as to reduce. a time required when a reception alarm signal is outputted till alarm diagnosis is finished. CONSTITUTION:An input signal (a) from a transmission line 1 is inputted an active reception section 2 and a standby reception section 3, from which reception section output signals b, c are outputted. When the signals b, c are received, a selector section 6 selects either of the signals b, c and outputs the result. The reception section 2 detects input interruption or pull out of frame synchronism and outputs a reception alarm signal (d) when the selector section 6 selects the signal (b), the reception alarm is diagnosed as to whether a cause to alarm is due to a fault of the transmission line 1 or a fault of the reception section 2. In this case, when the reception section 2 outputs the signal (d) and the reception section 3 does not output a signal (e), it is discriminated the reception section 2 is faulty and when the reception section 3 does not output the reception alarm signal (e), it is discriminated to be a fault of the transmission line 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line terminating circuit,
In particular, the present invention relates to a transmission line terminating circuit having a reception alarm diagnosis function in a receiving unit having a working system and a standby system in a data transmission device.

[0002]

2. Description of the Related Art Referring to FIG. 2, a conventional transmission line terminating circuit includes a working reception unit 12 and a standby reception unit 13 for receiving an input signal a from a transmission line 11, and a working reception unit 12 and a protection reception unit 12 for the transmission line 11. A switching unit 14 that switches and connects any of the spare reception units 13, a terminating resistor 15 that is connected to the input side of the active reception unit 12 and that terminates the transmission path 11, and a spare reception unit 13
16 which is connected to the input side of and terminates the transmission line 11
And a selector unit 17 which receives the receiving unit output signal b from the working receiving unit 12 and the receiving unit output signal c from the preliminary receiving unit 13 and selects one of them, and the working receiving unit 12 and the preliminary receiving unit 13. When any one of the input disconnection and the loss of frame synchronization is detected, the reception alarm signal d and the reception alarm signal e indicating the state are input and the switching control signal g for controlling the switching unit 14 and the selector control signal for controlling the selector unit 17 and a switching control unit 18 for generating f.

More specifically, the switching unit 14 includes a switching control unit 18
In response to the switching control signal g from the active receiver 12 or the standby receiver 13 is connected to the transmission line 11, and the input signal a from the transmission line 11 is output to the active receiver 12 or the standby receiver 13. To do. The working receiver 12 and the standby receiver 13 receive the input signal a from the transmission line 11 and output the receiver output signal b and the receiver output signal c. The selector unit 17, which receives the receiver output signal b and the receiver output signal c, selects either the receiver output signal b or the receiver output signal c in response to the selector control signal f from the switching controller 18. Output. The selector control signal f and the switching control signal g output from the switching control unit 18 are configured to select the same one of the active system and the standby system. That is, the switching control unit 18 outputs the switching control signal g for connecting the transmission line 11 and the working receiving unit 12 to each other.
When it is output to 4, the selector control signal f for selecting the reception unit output signal b is also output to the selector unit 17.
On the other hand, when the switching control unit 18 outputs the switching control signal g for connecting the transmission line 11 and the standby receiving unit 13 to the switching unit 14, the selector unit 17 also selects the receiving unit output signal c. The selector control signal f is output. The terminating resistors 15 and 16 are for terminating the transmission line 11, and the resistance value (R) is equal to the characteristic impedance of the transmission line 11. The input impedance when the terminating resistance 15 and the terminating resistance 16 of the working receiver 12 and the spare receiver 13 are removed is high impedance.

Now, when the working receiving unit 12 is connected to the transmission line 11 and the selector unit 17 selects the receiving unit output signal b from the working receiving unit 12, the working receiving unit 12 loses input or loses frame synchronization. When the reception alarm signal d that has detected the signal is output, the cause of this reception alarm is the transmission line 11
In order to determine whether the failure is due to the failure or the failure of the active receiver 12, the reception alarm diagnosis is performed. At this time, the switching control unit 18 receives the reception warning signal d, and the selector unit 1
7 and outputs the selector control signal f to the switching unit 14
The switching control signal g is output to the switching control signal g
Is input to the switching unit 14 and the transmission line 11 and the working receiving unit 12
And the connection between the transmission line 11 and the standby receiver 13 is switched. Therefore, the connection with the transmission line 11 is connected to the working reception unit 12
After switching from the standby reception unit 13 to the standby reception unit 13, the active reception unit 12 continues to output the reception warning signal d, and if the preliminary reception unit 13 does not output the reception warning signal e, the reason why the reception warning signal d is output Determines that the active reception unit 12 is out of order, and if the active reception unit 12 does not output the reception alarm signal d and the standby reception unit 13 does not output the reception alarm signal e, the reception alarm signal d is output. It is determined that the cause is a failure of the transmission line 11.

[0005]

In the conventional transmission line terminating circuit, the reception alarm diagnosis is performed when the reception alarm signal d or the reception alarm signal e is output from the active reception unit 12 or the standby reception unit 13. At this time, since the switching unit 14 performs the switching operation from the active receiving unit 12 to the standby receiving unit 13 or from the standby receiving unit 13 to the active receiving unit 12, the receiving unit on the switched side is separated from the transmission line 11 before the switching. Therefore, the input signal a input from the transmission line 11
The frame synchronization is lost, and it takes a predetermined time to establish the frame synchronization. Further, the switching operation in the switching unit 14 also requires a predetermined time. Therefore, one of the active reception unit 12 and the standby reception unit 13 outputs the reception warning signal d or the reception warning signal e, and then the other reception warning signal d or the reception warning signal e is output to perform reception warning diagnosis. There is a problem that it takes a long time from the occurrence of the reception alarm to the end of the determination before the execution. Furthermore, since a relay is used for the switching unit 14, there is a problem that the circuit scale increases and reliability decreases.

[0006]

A transmission line terminating circuit according to the present invention is connected in parallel to a transmission line as an active system and a backup system, receives signals from the transmission line at the same time, disconnects the input signal, and resets itself. The first and second means for respectively outputting the first and second detection signals when any one of the functional abnormalities is detected, and the first and second means, respectively, which are respectively connected to the transmission path side. Any of the third and fourth means for terminating the transmission line so that the impedance viewed from the first and second means sides becomes the same as the characteristic impedance of the transmission path, and the first and second detection signals. Switching means for outputting the switching control signal when the input signal is input, and not outputting the switching control signal when inputting both the first and second detection signals, and the first means. From receiving means When the first output signal and the second output signal from the second receiving means are input and the switching control signal in response to the first detection signal is input from the fifth means, the first output signal and the second output signal from the second receiving means are input. And a sixth means for selecting the first output signal when the switching control signal in response to the second detection signal is input from the fifth means.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. Referring to FIG. 1 showing an embodiment of the present invention, this transmission line terminating circuit has a working receiving unit 2 and a standby receiving unit 3 for receiving an input signal a from the transmitting line 1 and an input side of the working receiving unit 2. A terminating resistor 4 which is connected and terminates the transmission line 1, a terminating resistor 5 which is connected to the input side of the spare receiving unit 3 and terminates the transmission line 1, a receiving unit output signal b from the working receiving unit 2 and a preliminary receiving unit 3 A selector section 6 which receives the output signal c from the receiver and selects one of them is shown, and the state is shown when either the input disconnection or the loss of frame synchronization is detected in the active receiver 2 and the spare receiver 3. Received alarm signal d
And a switching control section 7 which receives a reception warning signal e and generates a selector control signal f for controlling the selector section 6.

More specifically, the input signal a from the transmission line 1 is branched into two and is input to the working reception unit 2 and the standby reception unit 3 which are constantly connected to the transmission line 1. The transmission line 1 is terminated by terminating resistors 4 and 5 connected in parallel. The resistance value (2R) of each of the terminating resistor 4 and the terminating resistor 5 is twice the characteristic impedance of the transmission line 1. The input impedance when the terminating resistance 4 and the terminating resistance 5 of the working receiver 2 and the spare receiver 3 are removed is high impedance. The working receiver 2 and the spare receiver 3 receive the input signal a from the transmission line 1 and receive the output signal b from the receiver.
And the receiver output signal c. Receiver output signal b
The selector unit 6 to which the receiver output signal c is input selects and outputs either the receiver output signal b or the receiver output signal c in response to the selector control signal f from the switching controller 7.

Now, when the selector section 6 is selecting the receiving section output signal b from the working receiving section 2, the working receiving section 2 detects an input disconnection or loss of frame synchronization and outputs a reception warning signal d. Then, the reception alarm diagnosis is performed to determine whether the cause of the reception alarm is due to the failure of the transmission line 1 or the failure of the active reception unit 2. At this time, if the standby receiver 3 does not output the reception alarm signal e when the active receiver 2 is outputting the reception alarm signal d, the reason why the reception alarm signal d is output is due to the fact that the reception receiver 2 outputs the reception alarm signal d. If it is determined that there is a failure, and if the standby receiving unit 3 outputs the reception warning signal e at this time, it is determined that the cause of the reception warning signal d being a failure of the transmission line 1. When it is determined that the reason why the reception warning signal d is output is due to the failure of the active reception unit 2, the switching control unit 7 receives the reception warning signal d and outputs the selector control signal f to the selector unit 6, In response to the selector control signal f, the selector section 6 selects and outputs the receiving section output signal c. However, when it is determined that the reason why the reception warning signal d is output is due to the failure of the transmission line 1 (that is, when the reception warning signal e is also output at this time), the switching control unit 7 receives the reception signal. Even if the alarm signal d and the reception alarm signal e are input, the selector control signal f is not output. Therefore, at this time, the selector unit 6 continues to select the receiving unit output signal b without selecting the receiving unit output signal c.

[0010]

As described above, according to the present invention,
Since a switching unit for the active system and the standby system is not provided, not only the time required from the output of the reception alarm signal to the end of the alarm diagnosis is shortened, but also the reliability is improved and the number of circuit components is reduced. You can

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a transmission line termination circuit according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional transmission line termination circuit.

[Explanation of symbols]

 1 Transmission line 2 Working receiver 3 Preliminary receiver 4, 5 Terminating resistor 6 Selector 7 Switching controller a Input signal b, c Receiver output signal d, e Reception alarm signal f Selector control signal

Claims (1)

[Claims] 1. An active system and a standby system, which are connected in parallel to each other in a transmission line and receive signals from the transmission line at the same time, and detect any one of an input disconnection of the signal and a malfunction of itself. At this time, first and second means for respectively outputting first and second detection signals, and each of the first and second means are respectively connected to the first and second means sides from the transmission path side. Third and fourth means for terminating the transmission line so that the observed impedance is the same as the characteristic impedance of the transmission line, and switching when any of the first and second detection signals is input Outputting a control signal, the first and second
The second control means does not output the switching control signal when both detection signals are input, and the first output signal from the first receiving means and the second output signal from the second receiving means. When the output signal is input and the switching control signal in response to the first detection signal is input from the fifth means, the second output signal is selected, and the fifth means selects the second output signal. And a sixth means for selecting the first output signal when the switching control signal in response to the detection signal is input.