JPH056810B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data transmission device, and particularly to an echo canceller type data transmission device that transmits data using a two-wire line.

[Conventional technology]

Generally, data transmission devices are equipped with a loopback circuit in order to easily diagnose and isolate failures. This loopback circuit uses the output of the transmitter as the input of the receiver, creates a loop within the data transmission device, and verifies the transmitted data with the received data, thereby making it possible to test the data transmission device. In this case, it is desirable to construct the loop close to the line in order to test as many functions of the data transmission device as possible. Therefore, in the case of a data transmission device using a two-wire line, it is usually constructed by utilizing simple unbalance of a hybrid circuit (four-wire two-wire conversion circuit) within the data transmission device.

[Problem that the invention seeks to solve]

However, in the conventional echo canceller type data transmission device, a desired loop cannot be formed because the transmitted signal that goes around to the receiving section via the hybrid circuit is canceled by the echo canceller. Therefore, a loopback circuit is configured by stopping the echo canceller function, but in this case, only a part of the functions of the data transmission device can be tested, and therefore it is not sufficient as a loopback circuit.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an echo canceller type two-wire full-duplex data transmission device that is capable of performing a sufficient loopback test.

[Means for solving problems]

The data transmission device of the present invention includes at least a transmitter that sends transmission data to a two-line line via a hybrid circuit, and a transmitter that transmits transmitter echo included in a received signal arriving from the two-line line via the hybrid circuit. A data transmission device including a pseudo echo generation circuit that generates a pseudo echo for cancellation, a subtracter that subtracts the pseudo echo from the received signal, and a receiver that reproduces received data from the output of the subtracter, A switch is provided that can select either the output of the subtracter or the output of the pseudo-echo generation circuit as an input to the receiver, and the output of the pseudo-echo generation circuit itself is used as an input signal to the receiver during testing. It was designed to be used.

[Effect]

In the present invention, by using the pseudo echo itself, which is the output of the pseudo echo generating circuit, instead of the received signal during testing, it is possible to configure a loopback circuit including the pseudo echo generating circuit.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

The drawing is a block diagram showing an embodiment of a data transmission device according to the present invention. In the figure, 1 is a transmitter that receives transmission data TD, 2 is a hybrid circuit, and 3 is a device that generates a pseudo echo that is a copy of the speaker's echo included in the received signal that arrives from the two-wire line 7 via the hybrid circuit 2. a subtracter 4 for subtracting the pseudo echo output from the pseudo echo generating circuit 3 from the received signal;
5 is a receiver, and 6 is a switch for selecting either the output of the pseudo echo generation circuit 3 or the output of the subtracter 4 as an input to the receiver 5.

Here, when the transmission data TD is input to the transmitter 1, this transmission data TD undergoes predetermined code conversion, waveform shaping, modulation, etc. in the transmitter 1, and then is transmitted to the two-wire It is sent to line 7. The received signal arriving from the two-wire line 7 via the hybrid circuit 2 and the talker's echo coming from the transmitter 1 via the hybrid circuit 2 are subtracted from the pseudo echo output from the pseudo echo generating circuit 3. After subtracting with 4, selector 6
This is the first input. Further, the pseudo echo becomes the second input of the switch 6, and the selected one of the first input and the second input is sent to the receiver 5, and the receiver 5 reproduces the received data RD. be done. At this time, the pseudo echo generation circuit 3 is connected to the transmitter 1.
This is an adaptive filter that receives the output of the subtracter 4 and the output of the subtracter 4, and generates a pseudo echo for canceling the speaker's echo. Therefore, when the apparatus is operating normally, the pseudo echo output from the pseudo echo generating circuit 3 is equal to the speaker's echo arriving from the transmitter 1 via the hybrid circuit 2 to the receiver.
As a result, during full-duplex communication, by causing the switch 6 to select the output of the subtracter 4, which is the first input, the device can be operated as a normal data transmission device. On the other hand, during a loopback test, by having the switch 6 select the output of the pseudo echo generation circuit 3 which is the second input, the speaker echo that loops from the transmitter 1 via the hybrid circuit 2 is sent to the receiver 5. The same effect as above can be obtained, and it is also possible to construct a loopback circuit including the pseudo echo generating circuit 3. Therefore, according to the present invention, since the pseudo echo itself of the pseudo echo generating circuit 3 is used instead of the received signal during testing, it is assumed that the received signal and the pseudo echo are normal, that is, the hybrid circuit 2, the pseudo echo generating circuit 3, and the subtraction signal. It is possible to test whether each of the devices 4 is normal.

〔Effect of the invention〕

As explained above, the present invention provides a switch that inputs either the output of the pseudo echo generation circuit or the output of the subtracter to the receiver, and the pseudo echo itself, which is the output of the pseudo echo generation circuit, is input to the receiver during testing. By using this as an input signal, it is possible to construct a loopback circuit including the pseudo echo generating circuit, that is, including the echo canceller section, so that a desired loopback test can be performed.

[Brief explanation of the drawing]

The figure is a block diagram showing one embodiment of the present invention. 1...Transmitter, 2...Hybrid circuit, 3...
...Pseudo echo generation circuit, 4...Subtractor, 5...Receiver, 6...Switcher, 7...Two-wire line.

Claims (1)

[Claims] 1 At least a transmitter that sends transmission data to a two-line line via a hybrid circuit, and a pseudo echo for canceling the speaker echo included in the received signal arriving from the two-line line via the hybrid circuit. A data transmission device including a pseudo echo generating circuit that generates a pseudo echo, a subtracter that subtracts the pseudo echo from the received signal, and a receiver that reproduces received data from the output of the subtracter. A switch is provided that can select either the output of the subtracter or the output of the pseudo-echo generation circuit, and the output of the pseudo-echo generation circuit itself is used as the input signal of the receiver during testing. data transmission equipment.