JPH0457543A - Loop back test control system for transmission line - Google Patents

Abstract

PURPOSE:To attain loop back test of each device connecting to a transmission line without need for a test code for loopback test by providing a switch controlling the DC transmission from a constant current source to the transmission line and a timer controlling the switch and a loopback switch with an output signal of a current detection circuit. CONSTITUTION:A DC current superimposed on a transmission line at a pre-stage is detected by a current detection circuit 201, and a timer 202 is detected, and an output of the timer 202 is given to a loop back switch 205, which is thrown to the position in dotted lines for a prescribed time to loop back the data. A test circuit 102 of a test device 108 confirms the coincidence between the sent data being the loop back data and a received data and a counter is incremented. After lapse of a prescribed time, the timer 202 throws the switch 205 to the position in dotted lines and controls a switch 204 to superimpose a DC current of a constant current source 203 onto a signal on the transmission line and a device of a next stage to the transmission line starts the loop back test. Thus, the loop back test of each device is conducted without a test code for the loop back test.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a digital data transmission system using bipolar signals, and more particularly to a test control system for performing loopback tests.

BACKGROUND OF THE INVENTION Conventionally, in this type of folding test method, a specific test code was determined for each folding device and a folding test was conducted.

For example, as shown in Fig. 3, in the case of a subscriber system with two relay devices 303 and 304 connected, four different test codes are required for each device, 302, 303, 304 and 305, to be sent from the tester 301. It was.

Problems to be Solved by the Invention The above-described conventional repeat test method has a drawback in that many types of test codes must be used in order to set a specific test code for each device.

To give an example, in FIG. 3, an in-office device 302, a relay bag! 303, the relay device 304, and the home device 305, four different test codes must be used for each device.

In addition, in order to search for a fault location, many types of test codes must be sent out one after another, and the search has the disadvantage of requiring time and effort.

The present invention has been made in view of the above-mentioned conventional situation,
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a novel loopback test control system for transmission lines that makes it possible to eliminate the above-mentioned drawbacks inherent in the conventional techniques.

Means for Solving the Problems In order to achieve the above object, the transmission line foldback test control method according to the present invention uses a constant current source that superimposes a direct current on the transmission line, and a A switch that controls direct current transmission to the transmission line and a test circuit that controls this switch and compares the transmitted signal and the received signal and counts the number of matches. a current detection circuit that detects the superimposed direct current; a constant current source that superimposes the direct current onto the transmission line; a switch that controls sending out the direct current from the constant current source to the transmission line; and a current detection circuit that detects the superimposed direct current. and a timer controlled by the output signal of the circuit.

Embodiment Next, a preferred embodiment of the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a block diagram of the inside of a tester according to the present invention.

In FIG. 1, transmission data is transmitted to a data transmission circuit 101.
The signal passes through the transmission transformer 106 and is transmitted to the outside of the tester. Further, the received data passes through the receiving transformer 107 and is received by the data receiving circuit 103. When performing a loop test, the test circuit 102 controls switch 1.
05 is operated to superimpose the DC current of the constant current source 104 onto the transmission path. The superimposed DC current triggers a loop test in the next stage device, as explained below.

Further, the test circuit 102 compares the data transmitted from the data transmitting circuit 101 and the data received by the data receiving circuit 103, and counts the number of times there is a match. That is, when performing a loopback test, the tester 108 has a function of superimposing a direct current on the transmission line on the transmitting side and comparing the returned data with the transmitted data.

FIG. 2 is a block diagram of a device that performs loopback, such as an in-office device, a relay device, and an in-home device.

When a loopback test is not performed, data from the tester side passes through the transmission transformer 206 and is sent to the next stage. Data in the opposite direction passes through the receiving transformer 207, passes through the return switch 205 set to the solid line side, and is sent to the next stage. When performing a loop test, the DC current superimposed on the transmission line by the previous stage is detected by the current detection circuit 201 and the timer 202 is detected. This timer 202
Set the return switch 205 to the dotted line side for a certain period of time,
Wrap data. The returned data is checked by the test circuit 102 of the tester 108 to confirm that the transmitted data matches the received data, and the counter is incremented.

After a certain period of time has elapsed, the timer 202 activates the return switch 20.
5 to the dotted line side, and further controls the switch 204 to superimpose the DC current of the constant current source 203 onto the transmission path.

This activates a loopback test in the device at the next stage of the transmission line.

FIG. 3 shows an example of a transmission system in which a loopback test is performed. This transmission system includes tester 301. It is composed of an in-office device 302, a relay device 303, a relay device 304, and an in-home device 305, and data is transmitted through transmission transmission paths 306, 308, 310, .
312 Also, reception transmission line 307.309.311.31
3 each.

Considering the explanations in FIGS. 1 and 2 and referring to FIG.
6 is returned to the transmission line 307, and the data from the tester 301
increases the loopback count by 1.

Next, after a certain period of time, the in-office device 302
When a DC current is superimposed on the relay device 303, the transmission line 30
8 is looped back to the transmission line 309.

The in-office device 302 transmits the data from the transmission path 309 to the transmission path 307 as is. Therefore, similarly, the tester 301
increases the loopback count by 1.

Similar operations are then performed by each device in the transmission path,
The number on the tester's counter records how many devices have returned calls.

From this number, it is possible to confirm how many devices the transmission line includes and whether the transmission line is normal.

As described in detail, according to the present invention, it is possible to perform a loopback test on each device connected to a transmission line without requiring any test cord for the loopback test. .

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram showing an embodiment of a tester in a transmission system of the present invention, and FIG. 2 is a block configuration diagram showing an embodiment of each of an in-office device, a relay device, and an in-home device in a transmission system of the present invention. FIG. 3 shows an embodiment of the transmission system of the present invention. 101...Data transmission circuit, 102...Test circuit,
103... Data receiving circuit, 104... Constant current source,
105...Switch, 106...Transmission transformer, 1
07... Receiving transformer, 108... Testing device, 201
...Current detection circuit, 202...Timer, 203.
...Constant current source, 204...Switch, 205...Return switch, 206...Transmission transformer, 207...
- Receiving transformer, 208... In-office device or relay device or in-home device, 301... Tester, 302... In-office device, 303.304... Repeater, 305... In-house device, 306308.310 .312...Transmission transmission line,
307.309.311.313...Receiving transmission line Patent applicant: NEC Co., Ltd. Representative Patent attorney Yutabe Kumagai 1o1: Data transmission route 102/Trial route 103° Data reception route 104: Fixed via K et al. Switch 106 + Transmission 18 Transformer 1o7゛ Receiving i Lance 108 - Tester Fig. 1 201: Current detection circuit 2α To timer 203: Constant current source 204 Near thousand Sochi 205: Return switch 206: Transmission transformer 207: Tori 208: In-station display and I-Go relay table 1 Nu IJ home arrangement Figure 2

Claims (1)

[Claims] In data transmission using bipolar signals, the test equipment uses a constant current source that superimposes DC onto the transmission line, a switch that controls sending DC from this constant current source to the transmission line, and a switch that controls and transmits the DC current from this constant current source. It has a test circuit that compares the signal and the received signal and counts the number of matches, and a current detection circuit that detects direct current superimposed on the transmission path in a loopback device, and a current detection circuit that superimposes the direct current on the transmission path. a constant current source; a switch that controls sending direct current from the constant current source to the transmission line;
A transmission line loopback test control method comprising: a timer that controls the switch and the loopback switch using an output signal of the current detection circuit.