JPH02159858A - Modem test system - Google Patents

Abstract

PURPOSE:To prevent inconvenience to switch to an exchange circuit during a loop test by transmitting information indicating the test execution when that the loop test is under execution is detected, and prohibiting the operation of a line switching part based on the information. CONSTITUTION:In a MODEM 1A, when a loop detecting part 1a detects that the line loop test has been activated, a transmitting part 2a outputs and transmits test start information to a sub-channel part 5b. In a MODEM 2B, a prohibiting part 1b prohibits the dial backup DBU function of a connection control part 8b by receiving the test start information from a sub-channel part 5b. Next, in the MODEM 1A, when the loop detecting part 1a detects the completion of the line loop test, the transmitting part 2a transmits test completion information. In the MODEM 2B, when the prohibiting part 1b receives the test completion information, it cancels the prohibition of the DBU function for the connection control part 8b.

Description

[Detailed Description of the Invention] [Summary] Regarding a test method for a modem having a dial backup function, the present invention provides a modem test method that can accurately perform a line loop test in a communication system connected by a modem having a dial backup function. A first modulator/demodulator that has a line switching unit that switches the connection to a switched line when an abnormality is detected in the connected dedicated line, and a looping unit that performs a loop test of looping back the output of the modulating unit to the demodulating unit. and a second modem having the line switching unit, the first modem includes means for detecting that the loop test is being executed, and based on the detection by the detecting means. means for transmitting information indicating that a test is being executed by the second modem, and means for prohibiting operation of the line switching section based on information from the transmitting means, If the device is running a loop test, the second
The modem is configured so that it does not switch to the switched line.

[Industrial Application Field] The present invention relates to a test method for a modem having a dial backup function.

BACKGROUND OF THE INVENTION Now that data communications have come to play an important function in all industrial fields, there is an increasing demand for means to continue communications without interruption. In recent years, in response to this demand, communication is usually carried out over a dedicated line, and when one modem detects a line abnormality, it automatically switches to the switched line and dials out, and the other modem is connected to the switched line and then dials the switched line. Dial backup (d
ial backup (DBU) function has become popular. Since modem failures can transmit erroneous data or disable communication, which can have a serious impact on business operations, there is a need for a modem testing method that can accurately detect failures even in modems with a DBU function. There is.

[Conventional technology]

One of the modem's self-diagnosis functions is to connect the modulation section and demodulation section on the line side of the modem, and check the data input to the modulation section and the data that is looped back and output to the demodulation section. A line loop test is widely and generally performed. However, in the conventional line loop test, a test looping back from the modulator to the demodulator is performed regardless of whether or not the modem has a DBU function.

[Problem to be solved by the invention]

As mentioned above, according to the conventional method, the line loop test is D
Regardless of the presence or absence of the BU function (because the modem loops back from the modulation section to the demodulation section on the line side, the transmission signal is not sent to the line during test execution, and under known line interface conditions, the receiving level of the other modem will decrease. If the modem on the other end is a modem set as the dialing side of the DBU function, an attempt will be made to connect to the switched line, but the modem running the line loop test will not respond, so it will not be possible to connect to the switched line. First, the other party's modem had the problem of repeating dialing.

SUMMARY OF THE INVENTION An object of the present invention is to provide a modem test method that can solve these problems and accurately perform a line loop test in a communication system connected by a modem having a DBU function.

[Means to solve the problem]

FIG. 1 shows a block diagram of the principle of the present invention.

In the figure, 1 is a first modulation/demodulation unit that has a line switching unit 18 that switches the connection to a switched line when an abnormality is detected in the connected dedicated line, and a looping unit 19 that performs a loop test by returning the output of the modulating unit to the demodulating unit. 2 is a second modem and a first modem having a line switching unit 28, 11 is means for detecting that a loop test is being executed; 12 is a means for detecting that a loop test is being executed; 12 is for executing a test based on the detection by the detecting means 11; In the second modem 2, 21 is a means for prohibiting the operation of the line switching section 28 based on the information from the transmitting means 12.

Therefore, while the first modem 1 is performing a loop test, the second modem
The modulator/demodulator 2 is configured not to perform switching to a switched line.

[Effect]

According to the invention, in the first modem 1 the detection means 1
1, when it is detected that the loop test is being executed, the transmitting means 12 transmits information indicating that the test is being executed;
In the second modem 2, the prohibition means 21 prohibits the operation of the line switching section 28 based on the information during the test execution, so that the second modem 2 is switched while the first modem 1 is executing the loop test. It is possible to prevent the inconvenience of switching to a line.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to FIG. The same reference numerals indicate the same objects throughout the figures.

Components in FIG. 2 that correspond to those in FIG. 1 are surrounded by dashed lines.

FIG. 2 is a block diagram showing an embodiment of the present invention,
The main structure of modems 1^ and 2B according to the present invention is shown.

In the modem l^, the main control section 4a controls each section to perform the functions of the modem IA.

The modulator 7m modulates the input business (user) data into the frequency band of the main channel and outputs the modulated data to the line. The frequency band of the line is the main channel (for example, 4800 bps
) and a subchannel (eg, 75 bps), each configured to transmit user data and line management information.

The demodulator 7d separates the main channel modulated signal from the line, demodulates it, and receives it.

The loopback section 9r connects the output of the modulation section 7m to the demodulation section 7d during a line loop test, and loops back the data input from the modulation section 7m to the demodulation section 7d.

The connection control unit 8a is normally connected to a dedicated line, and switches the connection to a switched line when the incoming call detection unit 8r detects an incoming call.

The sub-channel section 5a converts the input data into a signal in the frequency band of the sub-channel, and superimposes and synthesizes the signal on the signal in the frequency band of the main channel.

The loop detection unit 1a detects that the main control unit 4a starts and ends control of the line loop test based on instructions from an operation panel (not shown).

The transmitter 2a outputs test start information before starting the test based on the detection by the loop detector 1a, and outputs test end information after the test is completed to the subchannel unit 5a, and transmits the test end information to the modem 2B via the subchannel. .

In the modem 2B, the main control section 4b controls each section to perform the functions of the modem 2B.

The modulator 6m modulates the input user data into the frequency band of the main channel and outputs the modulated data to the line.

The demodulator 6d separates the main channel modulated signal from the line, demodulates it, and receives it.

The monitor part 8m monitors the reception level of the line and detects a line abnormality when it drops below a predetermined value.

The connection control unit 8b performs a DBU function to switch to a switched line when a line abnormality is detected in the dedicated line by the monitor part 8m, and connect the line by dialing to the modem 1^.

The subchannel unit 5b separates the subchannel modulated signal from the line, demodulates it, and receives it.

The prohibiting unit 1b prohibits the connection control unit 8b from using the DBU function when receiving the test start information via the sub-channel unit 5b, and cancels the prohibition when receiving the test end information.

Therefore, in the modem IA, when the loop detector 1a detects that the line loop test has been activated, the transmitter 2
a outputs test start information to the sub-channel section 5b and transmits it, and in the modem 2B, the prohibition section 1b outputs the test start information to the sub-channel section 5b.
By receiving the test start information from b, the DBU function is prohibited to the connection control unit 8b. Next, modem 1
In the modem 2B, when the loop detecting section 1a detects that the line loop test has ended, the transmitting section 2a transmits test end information, and in the modem 2B, the inhibiting section 1b receives the test end information and sends the message to the connection control section 8b. Against DB
Prohibition of Ui Noh.

It is configured to release the stoppage.

Subchannel data is normally relayed between multiple modems in order to be transmitted to multi-drop connected modems, but the modem that receives the test start and end information should not transmit it to subsequent modems. Therefore, the present invention can also be applied to multidrop lines.

Furthermore, although this embodiment shows an example in which the test start and end information is transmitted on the secondary channel, it goes without saying that it is also possible to scramble the test start and end information and transmit it on the main channel. Nor.

〔Effect of the invention〕

As explained above, according to the present invention, modem IA notifies modem 2B of the start of the test before executing the line loop test.
inhibits the DBU function, then modem JA notifies the test end at the end of the test, and modem 2B transmits DBtJ131.
Since the function is restored, it is possible to prevent an abnormality caused by the modem 2B detecting a drop in reception level and repeating switching to a switched line while the modem IA is executing a line loop test.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the principle of the present invention, and FIG. 2 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a first modem, 2 is a second modem, 18, 2B is a modem, 11 is a detection means, 1a is a loop detection section, 12 is a transmission means, 18.28 is a line switching section, 19.9r is a return unit, 21 is an inhibiting unit, 4a and 4b are main control units, 5a and 5b are sub-channel units, 6m and 7m are modulation units, 6d and 7d are demodulation units, 8a and 8b are connection control units, 8d indicates a dial section, and 8r indicates an incoming call detection section. 2a is the transmitting part, 1b is the prohibition part, 8I11 is a part of the monitor, Honsho Sun Moon Door J Rifle 099 Figure 1

Claims (1)

[Scope of Claims] A line switching unit (18) that switches the connection to a switched line when an abnormality is detected in the connected dedicated line, and a folding unit (19) that performs a loop test of looping back the output of the modulating unit to the demodulating unit.
) and the line switching unit (2).
8) in a communication system with a second modem (2) having: means (11) for detecting in the first modem (1) that the loop test is being executed; means (12) for transmitting information indicating that the test is being executed based on the detection by the means (11); Means (21) for prohibiting operation of the line switching unit (28)
and when the first modem (1) is performing a loop test, the second modem (1) is
A modem test method characterized in that the modem (2) does not switch to a switched line.