JPS6239924A - Data transmission equipment - Google Patents

Abstract

PURPOSE:To conduct sufficient loopback tests by providing a switch selecting either an output of a subtractor or an output of a pseudo echo generating circuit as the input of a receiver. CONSTITUTION:The pseudo echo generating circuit 3 inputs an output of a transmitter 1 and an output of a subtractor 4 and is an adaptive filter generating a pseudo echo to cancel a sender echo. When the unit is operated normally, a pseudo echo being an output of the circuit 3 is equal to a sender echo incoming to a reception section from the transmitter 1 via a hybrid circuit 2. Thus, the switch 6 selects the output of the subtractor 1 being the 1st input at full duplex communication so as to be activated as a conventional data transmitter. On the other hand, the switch 6 selects an output of the pseudo echo generating circuit 3 at loopback tests to constitute a loop back including the circuit 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data transmission device, and more 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 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 cross-codes the transmitted data and 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, the transmission signal that is sent back to the receiver via the hybrid circuit is canceled out by the echo canceller, making it impossible to form a desired loop. Therefore,
A loopback is configured by stopping the echo cancel 2 function, but in this case, only a part of the functions of the data transmission device can be tested, so it is not sufficient as a loopback circuit.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an echo canceller-based two-wire full-duplex data transmission device that allows sufficient loopback testing.

[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;
a pseudo-echo generation circuit that generates a pseudo-echo for canceling the sender's echo included in the received signal that arrives from the two-wire line via the hybrid circuit; and a subtracter that subtracts the pseudo-echo from the received signal. and a receiver that reproduces received data from the output of the subtracter, wherein either the output of the subtracter or the output of the pseudo echo generation circuit can be selected as an input to the receiver. It is characterized by being equipped with a switch.

[Effect]

In the present invention, by providing a switch that inputs either the output of the pseudo-echo generation circuit or the output of the subtracter to the receiver, a loopback circuit including the pseudo-echo generation circuit can be configured.

〔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 pseudo echo that is a copy of the speaker's echo included in the received signal that arrives from the two-wire line T via the hybrid circuit 2. a subtracter 4 that subtracts 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, the transmission data TD undergoes predetermined code conversion, waveform shaping, modulation, etc. It is sent to line 7. The received signal arriving from the two-wire line γ via the hybrid circuit 2 and the speaker's echo transmitted from the transmitter 1 via the hybrid circuit 2 generate a pseudo echo which is the output of the pseudo echo generating circuit 3. After subtracting with the subtracter 4, the first
becomes the input. Further, the pseudo echo is connected to the second input of the switch 6, and a selected one of the first input and the second input is sent to the receiver 5, and the receiver 5 receives the received data RD. will be played.

At this time, the pseudo-echo generation circuit 3 is an adaptive filter that receives the output of the transmitter 1 and the output of the subtracter 4 and generates a pseudo-echo for canceling the speaker's echo. Therefore, when the device is operating normally, the pseudo echo generating circuit 3
The pseudo echo which is the output of the transmitter 1 appears equally as the speaker's echo arriving at the receiving section via the hybrid circuit 2 from the transmitter 1. 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 generating circuit 3 which is the second input, the speaker's echo that is transmitted from the transmitter 1 via the hybrid circuit 2 can be transferred to the receiver 5. It is possible to obtain the same effect as when the signal is sent to the echo generator, and furthermore, it is possible to configure a loopback circuit including the pseudo echo generating circuit 3.

〔Effect of the invention〕

As explained above, the present invention includes a switch that inputs either the output of the pseudo echo generation circuit or the output of the subtracter as input to the receiver, and also includes the pseudo echo generation circuit.
Since it is possible to configure a loopback circuit including all the echo canceller sections, there is an effect that a desired loopback test can be performed.

[Brief explanation of drawings]

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, T...2 line line.

Claims (1)

[Claims] A transmitter that sends out at least transmission data via a hybrid circuit to a two-line line, and a pseudo echo that generates a pseudo echo included in a received signal that arrives from the two-line line via the hybrid circuit. a subtracter that subtracts the pseudo echo from the received signal; and a receiver that reproduces received data from the output of the subtracter; 1. A data transmission device comprising a switch that can select either the output of the echo generating circuit or the output of the pseudo echo generating circuit.