JP2931851B2 - Digital line station termination equipment and loopback test method for digital line station termination equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital transmission system in which a direct current is superimposed on a metallic line for signal transmission and power is supplied from a station to a terminal in a digital transmission system using a metallic subscriber line. The present invention relates to a test apparatus used for diagnosing a failure in a terminal device in a line station and a test method thereof.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram of this type of digital channel station (Office Channel Unit, hereinafter referred to as OCU). In the figure, OCU
Are a line termination circuit 1, a transmission line termination circuit 2, a loop folding circuit 3, a power separation filter 4, a loop current detection circuit 5, and a power supply circuit 6 for long-distance power supply to the two-line subscriber line 8. And a start switch 7. It is to be noted that the remote power supply power supply circuit 6 does not necessarily need to be a component of the OCU (it may be arranged outside the OCU).
This example shows a case where the device is arranged in the OCU.

The digital signal transmitted from the intra-station equipment 9 passes through a line termination circuit 1, a transmission line termination circuit 2, a loop return circuit 3, a power separation filter 4, a start switch circuit 7, and a two-subscriber line 8 Output to Conversely, the transmission digital signal from the two-line subscriber line 8 is output to the intra-station device 9 following the above-described reverse path. The terminal-side power supply DC current is supplied by a remote power supply power supply circuit 6, a loop current detection circuit 5 for detecting that the 2-wire subscriber line 8 has become DC conductive, a power separation filter 4, and a start switch. The signal is output to the two-line subscriber line 8 via the circuit 7. In the start switch circuit 7, N1, N2, R1 and R2 are switches, and function to invert the polarity of the power supply voltage. That is, when NI = N2 = ON and R1 = R2 = OFF, normal polarity (L1: positive polarity, L2: negative polarity), NI = N2
= Off and R1 = R2 = on when reverse polarity (L
1: negative polarity, L2: positive polarity), which are applied to the two-line subscriber line 8.

In the loop wrap test, the loop wrap circuit 3 is operated to loop the transmission digital signal by the loop wrap control signal 13. That is, the input digital signal from the intra-station device 9 is transmitted to the line termination circuit 1,
The signal is looped back by the loop loop-back circuit 3 via the transmission line termination circuit 2, and is output to the intra-office device 9 via the transmission line termination circuit 2 and the line termination circuit 1. Then, the in-station device side 9
The normal operation of the OCU is confirmed by comparing the digital signal folded back in with the digital signal input to the OCU.

[0005]

In the conventional loop-back test, since the above operation is performed, the OCU shown in FIG.
Of the circuit blocks, the normal operation of the signal transmission system circuits, that is, the line terminating circuit 1, the transmission line terminating circuit 2, and the loop turning circuit 3 can be confirmed, but other circuit blocks in the OCU, that is, the power supply circuit 6 for distant power supply, There is a disadvantage that the normal operation of the station power supply system circuit including the loop current detection circuit 5, the power separation filter 4, and the start switch circuit 7 cannot be confirmed. Therefore, an object of the present invention is to provide an apparatus and a method capable of testing even a normal operation of a station power supply system circuit at the time of a loop return test.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a digital circuit through a two-wire metallic line.
Digital communication with line home connection device and OCU
And from the OCU via a two-line metallic line
DC power supply to the digital network home connection equipment
In a communication system, an OCU is an externally located station.
Digit based on loop return control signal from internal device
Fold the digital signal transmitted toward the home connection equipment
Loop loop-back circuit and digital circuit
DC current supplied to equipment and flowing on 2-wire metallic line
Loop current detection circuit that detects the presence or absence of
Start switch that can reverse the polarity of DC voltage
Circuit and receives a loop return control signal .
And means for initiating the folding of the transmission digital signal after confirming the normal operation of the signal and starting switch circuit, the start switch circuit as DC loop in the OCU is formed to confirm the normal operation of the starting switch circuit of
When a pair of switches are turned on, the pair of switches are turned on.
After the switch is turned on, turn off this pair of switches one by one.
Means for controlled so, formation and the electromotive force of the DC loop
Means for confirming the result of the control of the switch of the dynamic switch circuit by the judgment result of the loop current detection circuit. The OCU includes a loop-back circuit and a loop power supply.
A flow detection circuit and a start-up switch circuit are provided.
If a control signal is received, a DC loop is formed in the OCU
Turn on a pair of switches in the start switch circuit
And after turning on the pair of switches,
Control to turn off the switches one by one.
Formation of flow loop and control of switch of start-up switch circuit
Is detected by the loop current detection circuit.
After confirming the normal operation of the startup switch circuit,
Perform a loop-back test on the transmitted digital signal.
It is a method.

[0007]

When the loop return control signal is received, the start switch circuit operates independently, each switch of the start switch circuit is opened and closed so that a DC loop is formed in the OCU, and this DC loop is formed. It is detected by the loop current detection circuit. Then, according to this detection result, after the normal operation of the station power supply system circuit such as the start switch circuit is confirmed, a loop folding test of the transmission digital signal is performed. As a result, the normal operation of all circuit blocks in the OCU is confirmed.

[0008]

EXAMPLE Table 1 is a table showing test control contents of the present invention.

[0009]

[Table 1]

In the table, each test (tests 1 to 7)
3 shows the contents of a start switch control signal 11 issued from the line termination circuit 1 to the start switch circuit 7 and a test result (a detection result judgment signal 10 of the loop current detection circuit 9) for which the test is judged to be normal. That is, for example, in test 1, if the loop current detection result determination signal 10 is on in response to the control signal 11 to the start switch circuit 7 that R1 = N1 = on and R2 = N2 = off, this test is normal. That is, the DC station power supply current output from the remote power supply power supply circuit 6 passes through the loop current detection circuit 5, the power separation filter 4, and further forms a DC loop via the R 1 and N 1 of the start switch circuit 7. I do. This result is detected by the loop current detection circuit 5 and sent to the line termination circuit 1 as a detection result determination signal 10 of the loop current detection circuit 5. Hereinafter, tests 2 to 7 are similarly performed.

Next, FIG. 2 is a flow chart for explaining the operation of the embodiment of the present invention, and explains the operation of the procedure of the tests 1 to 6 shown in Table 1. The loop termination control signal 13 from the intra-station device 9 is received by the line termination circuit 1 so that the line termination circuit 1 autonomously controls each switch in the start-up switch circuit 7 according to the procedure shown in FIG. In FIG. 2, test j (j = 1 to 6) corresponds to tests 1 to 6 in Table 1. In FIG. 2, when it is determined that any of the tests 1 to 6 is abnormal (NG: does not match the loop current detection result determination signal 10 determined to be normal operation shown in Table 1), the procedure proceeds to A. In A, the loop termination drive signal 12 is not issued from the line termination circuit 1 to the loop return circuit 3 and the circuit continues to wait. As a result, since the transmission digital signal is not looped back, the apparatus which issues the loop looping control signal 13 to the local station apparatus 9 determines that the loop looping is defective, and the loop looping control signal 13
Is canceled, and it is determined that the OCU is defective.

Next, in FIG. 2, when it is determined that tests 1 to 6 are normal (OK: when it matches the loop current detection result determination signal 10 which is determined to be normal operation shown in Table 1), the procedure proceeds to B. Advances. In B, the station power supply circuit system in the OCU is determined to be normal, and then the loop termination drive signal 12 is issued from the line termination circuit 1 to return the transmission digital signal. A normal operation of the signal transmission circuit in the OCU can be determined by determining the folded digital signal on the in-station device 9.

In a communication system designed to supply a current to the digital circuit home connection unit (DSU) via the two-line subscriber line 8 with the reverse polarity and not to supply the current with the normal polarity, FIG. At the time of transition to B of 2, the test 7 is executed before driving the loop folding,
If the determination result is abnormal, it is possible to confirm a short-circuit state in eight sections of the two-line subscriber line.

As described above, according to the present invention, when the loop termination control signal 13 is received by the line termination circuit 1, the line termination circuit 1 operates the start switch circuit 7 autonomously, and the switches N1, N2, OCU for R1 and R2
The start switch circuit 7 and the power separation filter 4, the loop current detection circuit 5, and the remote power supply power supply circuit 6 are opened and closed so that a DC loop is formed therein, and by confirming that the DC loop is formed. After the normal operation is confirmed, the loop back of the transmission digital signal is performed, so that the normal operation of all the circuit blocks of the OCU is confirmed by the loop back test.

[0015]

As described above, the loop-back test apparatus and test method for a terminal unit in a digital line station according to the present invention can be used in a loop-back test. This has the effect of enabling testing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart illustrating the operation of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Line termination circuit 2 Transmission line termination circuit 3 Loop return circuit 4 Power separation filter 5 Loop current detection circuit 6 Remote power supply power supply circuit 7 Startup switch circuit 8 2-line subscriber line 9 Local station side 10 Loop current detection result judgment signal 11 Start switch control signal 12 Loop return drive signal 13 Loop return control signal

Claims (2)

(57) [Claims] 1. A digital line home connection device and a digital line station termination device are opposed to each other via a two-line metallic line to perform digital communication, and the digital line station termination device is connected to the digital line station via the two-line metallic line. in digital line communication system for performing a station power feeding from the DC to the home connection device, wherein the digital line station terminating device, the transmission digital to the digital line home connection device direction by loop folding control signal from the intra-station apparatus which is disposed outside A loop return circuit for returning a signal, a loop current detection circuit for detecting the presence or absence of a DC current supplied to the digital line home connection device and flowing on the two-wire metallic line,
A start switch circuit capable of reversing the polarity of the DC voltage supplied to the station, and upon receiving the loop return control signal, confirms the normal operation of the start switch circuit and then starts returning the transmission digital signal. means and, 1 of the activation switch circuit so that the DC loop is formed by the digital line station terminating device in order to verify the correct operation of the activation switch circuit
Turning on the pair of switches and the pair of switches
Turn off this pair of switches one by one after turning on
And means for controlling the formation of the DC loop and the activation
Means for confirming the result of control of the switch of the switch circuit by the judgment result of the loop current detection circuit. 2. A digital line home connection device and a digital line station termination device are opposed to each other via a two-line metallic line to perform digital communication, and the digital line station termination device is connected to the digital line station via the two-line metallic line. in digital line communication system for performing a station power feeding from the DC to the home connection device, wherein the digital line station terminating device, the transmission digital to the digital line home connection device direction by loop folding control signal from the intra-station apparatus which is disposed outside A loop return circuit for returning a signal, a loop current detection circuit for detecting the presence or absence of a DC current supplied to the digital line home connection device and flowing on the two-wire metallic line,
E Bei an activation switch circuit capable of reversing the polarity of the DC voltage to be a station feeding, the activation switch circuit so that the loop folded control signal reception result the digital line station terminating device in a direct current loop is formed Of 1
Turning on the pair of switches and the pair of switches
Turn off this pair of switches one by one after turning on
By controlling the formation of the DC loop and the activation switch
The control result of the switch of the switch circuit is detected by the loop current detection circuit, and after the normal operation of the start switch circuit is confirmed in accordance with the detection result, a loop folding test of the transmission digital signal is performed. Test method for loopback of terminal equipment in digital circuit station.