JPS5911225B2 - Remote measurement method for receiving sensitivity level of data communication equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for telemetry of the reception sensitivity level of a data communication device.

In general, in order to prevent erroneous output due to noise in the event that the receiving power is lost due to some reason such as a transmission line failure, data communication equipment assumes that reception has been interrupted when the reception level falls below a predetermined value and sends the signal to the output device. It has a function to stop or hold output.

A carrier wave detection circuit is normally used as a means to identify whether the reception level exceeds a predetermined threshold (reception sensitivity level), but the reception sensitivity level may change due to aging of this type of detection circuit. Naturally, the operating characteristics of the data communication device deteriorate. Therefore, it is often necessary to check whether the reception sensitivity level of a data communication device is normal, but this involves the difficulty of requiring a maintenance person to travel to a distant data terminal. . On the other hand, as a method for remotely measuring the operating characteristics of a large number of data terminals scattered far away from a center, a return loop is formed within the data terminal under test based on commands from the center, and a test pattern is sent back at the center. A loopback test method is known that measures code errors by comparing signal patterns. Unfortunately, such a test method cannot measure the reception sensitivity level of the data communication device on the terminal side. The present invention has been made in view of the above points, and its first object is to provide a telemetry method that can automatically remotely measure the receiving sensitivity levels of scattered data terminals from a center.

Another object of the present invention is to provide a telemetry method that allows the above-mentioned telemetry to be performed in response to commands from the terminal side, and further allows the telemetry to be performed between connected terminals without going through a center. There is a particular thing. The present invention achieves the above objects,
A loopback test state is established between the first and second data communication devices connected via the data line, and then the first
The reception sensitivity level of the second communication device is remotely measured by gradually decreasing the transmission level of the second data communication device and measuring the transmission level just before the first data communication device loses reception.

Hereinafter, further details of the present invention will be explained with reference to Examples. The figure is a functional block diagram of one embodiment of the present invention. 10 is a data communication device on the center side, 20 is a data communication device on the terminal side, 30 is a data line, 11p21 is a control device, 12,
22 is a modulation circuit, 14, 24 is a demodulation circuit, 13, 16,
Reference numerals 23 and 26 are band-pass P-wave devices, 15 and 25 are amplitude control circuits, 17p and 27 are carrier detection circuits, and 18 is a variable attenuation circuit.

The control device 11 on the center side collectively shows all the parts in the data communication device 10 except for the modulation/demodulation section, and is composed of a communication control device, a central processing unit, an input/output device, and the like. Similarly, the control device 21 on the terminal side is shown collectively with all the parts in the data communication device 20 except for the modulation/demodulation section, and is composed of a transmission control device, an input/output control device, an input/output device, etc. There is. Center side control device 1,
The loopback test command issued by the controller 1 is modulated by the modulation circuit 12, transmitted via the data line 30, demodulated by the demodulation circuit 24 on the terminal side, and then sent to the loopback test command detection circuit built in the control device 21. Detected in

The control device 21 that has detected this command forms a return loop within itself and detects the R signal based on the CD (Carrier Detect) signal received from the carrier wave detection circuit 27.
The S (RequesttOSend) signal is turned on to operate the modulation circuit 22, and the test pattern sent from the center following the loopback control command is sent back to the center via the data line 30. Upon receiving this, the carrier detection circuit 17 on the center side outputs a CD signal, and the control device 11 that received this CD signal performs a loopback test by comparing the return test pattern input from the demodulation circuit 14 with the sent test pattern. Know that the condition has been established. Once this test condition is established, the controller 11 applies an AT signal to the variable attenuator 18.

This AT signal is a signal whose amplitude changes at an appropriate speed, so that the insertion loss of the variable attenuator 18 gradually increases and the transmission level from the center 10 gradually decreases. Along with this, the reception level on the terminal side 20 gradually decreases, and when this value exceeds the reception sensitivity level of the carrier detection circuit 27 in the data communication device 20 of the terminal, the carrier detection circuit 27 determines that the reception has been interrupted. and turn off the CD signal. When the control device 21 detects that the CD signal is turned off, it immediately changes the RS signal to the modulation circuit to OFF and stops sending the signal back to the center side. As a result, the carrier detection circuit 17 on the center 10 side detects the reception interruption and turns off the CD signal to the control device 11. The control device 11 measures the value of the AT signal at the time when the CD signal is turned off, and calculates the transmission level immediately before reception is interrupted based on the preset relationship between the AT signal value and the transmission level. The control device 11 calculates the receiving sensitivity level of the terminal under test 20 by subtracting the pre-recorded transmission loss amount of the data line from the above-mentioned calculated value of the transmission level, and types it out to the terminal device. . If the reception sensitivity level of the terminal measured in this way deviates from the nominal value (eg -38 dBm at 200 bits/second) by more than a predetermined value, it is determined that adjustment on the terminal side is required.

The rate of decrease in the transmission level on the center side is set to an appropriate value depending on the data transmission speed, etc., but at least it must be slow enough to match the carrier detection (CD) time, transmission request (RS) time, etc. on the terminal side. An example of the AT signal that must be used is one that integrates the CD signal of the carrier wave detection circuit 17,
In this case, the transmission output on the center side decreases linearly with time. Although the example in which the loopback test command is issued from the center side has been described above, it is clear that the loopback test command may also be issued from the terminal side.

Further, although an example has been described in which one of the data communication devices is on the center side, it is clear that the above-described telemetry can be performed between data communication terminals that are connected without going through a center. As described above, according to the present invention, since the loopback test function of the conventional device is utilized, remote measurement of the receiving sensitivity level can be realized by adding only a small amount of hardware.

Further, the present invention is particularly effective when the receiving sensitivity level of a large number of scattered remote data terminals is remotely measured from the center side.

[Brief explanation of the drawing]

The figure is a functional block diagram of one embodiment of the present invention. 10...Data communication device on the center side, 20.-
...Terminal side data communication device, 30... Data line, 11, 21... Control device, 12, 22
... Modulation circuit, 14, 24 ... Demodulation circuit, 17, 27 ... Carrier detection circuit, 18 ...
...Variable attenuation circuit.

Claims (1)

[Claims] 1 Establishing a loopback test state between first and second data communication devices connected via a data line, followed by gradually decreasing the transmission level in the first data communication device. , a step of stopping the signal return to the first data communication device when the reception level in the second data communication device falls below a predetermined value; and thereafter, the second data communication in the first data communication device 1. A telemetry method for receiving sensitivity level of a data communication device, comprising the steps of detecting stoppage of signal return from the device and detecting its own transmission level at the time of detection.