| 摘要 |
<p>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.</p> |
