JPS587729Y2 - modem - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a modulation/demodulation device having an amplitude equalizer and a line folding test function.

An example of a conventional device of this type is shown in FIG. 1 and will be explained as follows.
In the figure, 1 is a modulation section, 2 is a demodulation section, 3 is an amplitude equalizer that receives the output of the modulation section 1, 4 is an amplitude equalizer connected before the demodulation section 2, 5, 6.7 and 8 are interlocking line return test switches, 9 is an output terminal, and 10 is an input terminal.

When the test switches 5 to 8 are in a normal communication state as shown in the figure, the output of the modulator 1 is obtained at the output terminal 9 via the amplitude equalizer 3 and the normally closed contacts of the switches 5 and 7 in series. In addition, an external input signal applied to the input terminal 10 enters the demodulator 2 via the normally closed contacts of the switches 8 and 6 and the amplitude equalizer 4 in series, and is demodulated. It is configured.

On the other hand, when the test switches 5 to 8 are in the test state, the output of the modulator 1 enters the demodulator 2 via the amplitude equalizer 3, the normally open contacts of the switches 5 and 6, and the amplitude equalizer 4 in series. It is configured to be demodulated and perform local testing.

In this test state, the input signal applied to the input terminal 10 from the outside is configured to be sent back to the other party via the normally open contacts of the switches 8 and 7 and the output terminal 9 in series. .

FIG. 2 is a circuit diagram showing an example of a conventional amplitude equalizer used in the modulation/demodulation device shown in FIG. 1, and shows only the parts necessary for explanation.

In the figure, 11 is an input terminal, 12 is a connection switching section constituting means for selecting an amplitude equalization characteristic, 13 is an input circuit section,
14 is an operational amplifier whose input is the output of the input circuit section 13;
15 is a feedback circuit unit connected between the output end and the input end of the operational amplifier 14; 16 is a connection switching unit constituting means for selecting the amplitude equalization characteristic similarly to the connection switching unit 12; and 17 is an output terminal. It is.

Here, C, Q, P, and N in the connection switching sections 12 and 16 constituting the characteristic selection means are strap terminals.

FIG. 3 shows the amplitude equalization characteristic shown in FIG. 2 and used to explain the operation of the present invention, and a shows the amplitude equalization when the strap terminals C and Q are connected in the connection switching section 12.16 constituting the characteristic selection means. b shows the characteristics of the amplitude equalizer when strap terminals C and P are connected, and C shows the characteristics of the amplitude equalizer when strap terminals C and N are connected, respectively.

Now, FIG. 1 shows a normal communication state, which is not a test state, and the amplitude equalizer 3 corrects the amplitude characteristics of a transmission path (not shown) connected to the output terminal 9. Appropriate straps are attached to the connection switching sections 12 and 16 constituting the characteristic selection means.

On the other hand, the amplitude equalizer 4 similarly corrects the amplitude characteristics of a transmission path (not shown) connected to the input terminal 10.
Connection switching units 12 and 16 constituting the characteristic selection means shown in the figure
A suitable strap is provided.

It is assumed that the same applies to the modulation/demodulation device facing the present device shown in FIG.

In communication under such conditions, the amplitude characteristics of the transmission path are corrected, so the signal from modulator 1 is correctly demodulated by the demodulator of the opposing modulator and demodulator, and the signal from the modulator of the opposing modulator and demodulator is correctly demodulated. The signal is correctly demodulated by the demodulator 2.

However, in a device with such a configuration, the line folding test is performed by switching switches 5, 6, 7, and 8, so the output signal of modulator 1 is transmitted to amplitude equalizer 3, switches 5, and 6. , is led to the demodulator 2 via the amplitude equalizer 4, but since there is no transmission path on the way, the amplitude equalizers 3 and 4 result in an over-equalization state, and the demodulator 2 has the disadvantage that it generates a code error. was there.

Conventionally, in order to eliminate such drawbacks, in the case of line folding tests, the characteristics of the amplitude equalizers 3 and 4 are reset to be flat, or the signals are not passed through the amplitude equalizers 3 and 4. Measures are being taken to do so.

However, in the former means for flattening the characteristics, as is clear from the circuit of FIG. In addition, it has the disadvantage that it must be restored to its original state again after the test, and there is a risk of a restoration error.

On the other hand, in the latter method of not passing signals through the amplitude equalizer, from the point of view of the self-test (local test) of the modulator/demodulator, which is the purpose of the line loop test, it is not possible to remove the amplitude equalizers 3 and 4. The drawback was that the test became less meaningful.

In view of the above points, the present invention was devised to solve such problems.The purpose of this invention is to be able to correctly perform a line folding test that does not depend on the set amplitude equalization characteristics in a short time, and to An object of the present invention is to provide a modulation/demodulation device that includes an amplitude equalizer in its test loop and can confirm that the amplitude equalizer operates correctly.

Hereinafter, the configuration and the like will be explained in detail with reference to the illustrated embodiments.

FIG. 4 is a block diagram showing an embodiment of a modulation/demodulation device according to the present invention.

In FIG. 4, the same reference numerals as in FIG. 1 indicate corresponding parts, and 18 and 19 are switches connected to the amplitude equalizers 3 and 4, respectively, and controlled by the line folding test switches 5 to 8.

Here, the difference from FIG. 1 is that the amplitude equalizers 3 and 4 each have a switch 1 controlled by switches 5 to 8.
8.19 is provided, and the purpose of this switch 18.19 is to control the amplitude equalizers 3 and 4 so as to have flat characteristics during a line folding test.

FIG. 5 is a circuit diagram showing an example of the amplitude equalizer in the embodiment of FIG. 4.

In FIG. 5, the same parts as in FIG. 2 are given the same reference numerals, and their explanation will be omitted.

20 is a relay controlled by the switch 18 in FIG. 4, 21 is a normally open contact of the relay 20, and 22 is a normally closed contact of the relay 20.

The normally open contact 21 is connected between the input end of the connection switching section 12 constituting the characteristic selection means and the output end of the input circuit section 13, and the normally closed contact 22 is connected between the feedback circuit section 15 and the ground. It is connected to the.

Next, the operation of the embodiment shown in FIG. 4 will be explained with reference to FIG. 5.

First, in FIG. 4, switches 5 to 8 and 18 and 1
9, the modem performs a line loop test.

Next, in FIG. 5, before the switch 18 is operated, the amplitude equalization characteristic is as shown in characteristic a of FIG. 3.

In this state, switch 18 is used for a line loop test.
When the switch is closed and turned ON, the relay 20 operates and its normally closed contact 22 is opened. This is equivalent to the case where the section 15 is connected to the strap terminal CN, and it is as if the connection switching section 16 is connected to the strap terminal CN.

Furthermore, at the same time, the normally open contact 21 of the relay 20 is closed, so that the input circuit section 13 is connected to the strap terminal C-Q even though the connection switching section 12 constituting the characteristic selection means is connected to the strap terminal C-Q. This is equivalent to connecting to strap terminal C-N.

That is, even if the straps of the connection switching units 12 and 16 constituting the characteristic selection means are either CQ or C-P, by closing the switch 18, the amplitude equalization characteristic can be changed to characteristic C in FIG. It is possible to obtain flat characteristics as shown.

As is clear from the above, in Figure 4,
When the switches 18 and 19 are operated, the amplitude equalizer 3
and 4 have flat characteristics.

That is, when moving to the line return test, the modulation section 1
The signal passes through amplitude equalizers 3 and 4, but is correctly demodulated by demodulator 2 without waveform distortion.

Although the present invention has been described above using an example in which the characteristics of the amplitude equalizer are controlled by a relay controlled by the switch 18 or 19, the present invention is not limited to this. It is also possible to use one set of switch closing contacts and one set of opening contacts in conjunction with switches 5-8 and 18.19.

It goes without saying that the switches 18 and 19 may be switches made of active elements controlled by the switches 5 to 8.

As described above, according to the present invention, there is no need to change the connection of the amplitude equalizer selection means in the line folding test.
There is no loss of time and no return errors occur when returning to the original state.

Moreover, since the line loopback test passes through the amplitude equalizer, it becomes possible to test the entire modulation/demodulation device, and the drawbacks of conventional modulation/demodulation devices are solved.

As explained above, according to the present invention, when performing a line folding test on a modulation/demodulation device with a built-in amplitude equalizer, the amplitude There is no need to change the connection of the equalizer selection means, and time loss is eliminated, so the practical effect is extremely large.

In addition, since there is no need to restore the amplitude equalizer selection means after the line loop test is completed, there is no risk of a reset error, and the entire modulation/demodulation device including the amplitude equalizer can be tested. Extremely effective.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an example of a conventional modulation/demodulation device, Fig. 2 is a circuit diagram of the amplitude equalizer in Fig. 1, Fig. 3 is an operation explanatory diagram showing the characteristics of the amplitude equalizer, and Fig. 4 5 is a block diagram showing an embodiment of the modulation/demodulation device according to the present invention, and FIG. 5 is a circuit diagram showing an example of the amplitude equalizer in FIG. 4. 1...Modulation section, 2...Demodulation section, 3, 4
......Amplitude equalizer, 5-8, 18.19...
··switch.

Claims (1)

[Scope of utility model registration request] In a modulation/demodulation device having a first amplitude equalizer receiving the output of the modulation section as an input, and a second amplitude equalizer provided before the demodulation section, and having a line folding test function, A second switch controlled by the first switch forming a test loop is provided in each of the first and second amplitude equalizers, and during a line return test, the first and second amplitude equalizers are controlled based on the operation of the second switch. 1. A modulation/demodulation device characterized in that each of the amplitude equalizers is controlled to have a flat characteristic.