| 摘要 |
PURPOSE:To make it possible to take an advanced circuit test in a simple method by detecting the electric current or voltage of the subscriber's line of a time-division telephone switch-board and then by transferring the detection data to a testing device by way of a coder and time-division switch. CONSTITUTION:Once an incoming signal arrives at subscriber's telephone set 1, an inversion command signal is applied to DC output inversion command terminal 37 of audio output amplifier 28 and by way of subscriber's line 2 and capacitor 15 of telephone set 1, a calling signal is applied by the DC output of amplifier 28 to bell 14 of telephone set 1, putting bell 14 into operation. Simultaneously with the operation, calling signal current is detected by diodes 23 and 25 of the photocoupler of two-wire/four-wire converting circuit 7, whose outputs are sent to transistor parts 24 and 26 of reception part 27 on the four-wire output side and then added by differential amplifier 31 by way of earth switches 29 and 30. The output of amplifier 32; and the output of circuit 33 is sent to output terminal 34 and that of amplifier 23 is converted by coder 8 into a digital signal, which is applied to a testing device by way of time-division switch 10. |
