| 摘要 |
PURPOSE:To allow an exchange station to confirm the loop connecting state of a digital telephone set directly by operating a switch having an off-hook function at test sequence detection to close the loop, setting a loop path to an information channel and displaying it on a display device which is under test. CONSTITUTION:In conducting the loop test, a DSU3 is operated from an exchange 1 to apply a voltage to a digital telephone set 4. When the digital telephone set 4 receives an incoming signal from the exchange 1, a confirming signal is returned and the exchange 1 receiving the confirming signal transmits a test signal. When the digital telephone set 4 receives a test signal, the digital telephone set 4 confirms it to be a loop test by a signal control circuit 12, transmits a test confirming signal and turns on an electronic switch 6 via a control line (a). Further, the circuit 12 actuates a selector circuit 21 to conduct the loop test for an information channel, transmits a response signal via the selector circuit 21 setting the loop bus and displays it on a display device 20 which is under test. |
