| 摘要 |
PURPOSE:To stabilize a call signal, by detecting opening or closing of semiconductor switches and using an exclusive operating circuit to prevent the simultaneous operation in a circuit for transmission of the call signal to a subscriber's terminal of a telephone exchange. CONSTITUTION:Conduction or nonconduction of p-n-p-n transistors TRs 11a, 11b, 12a, and 12b constituting semiconductor switches is detected by a detecting circuit 13c, and the detection output is transmitted as one of control information to a controlling circuit 14, and an exclusive opeating circuit 13 for delay circuits 13a and 13b having delay times longer than the turn-off time of p-n-p-n TRs 11a, 11b, 12a, and 12b is used to prevent the simultaneous operation of two semiconductor switches 11 and 12. Consequently, a stable circuit is obtained where a call signal source 5 and the earth do not collide. |
