PURPOSE: To simplify a call signal switching circuit for a subscriber's terminal and to prevent influence such as noises exerted upon other circuits by preventing a call signal with high voltage from direct switching.

CONSTITUTION: When a call signal is to be sent to a subscriber's terminal 5, a call signal generating circuit 3 is previously stopped by a control device 2. When the level of the call signal is sufficiently lowered, a switching circuit 4 is driven from the device 2. When the circuit 4 is completely turned to the circuit 3 side, the circuit 3 is started by the device 2 to send the call signal (e) to the terminal 5. When the sending of the call signal is to be stopped, the circuit 3 is stopped by the device 2, when the level of the call signal is sufficiently lowered, the circuit 4 is restored by the device 2, and when the circuit 4 is completely turned to the exchange circuit network 1 side, the circuit 3 is started again by the device 2. If a call signal is to be sent to another subscriber's terminals, a terminal 7 e.g., a switching circuit 6 is driven and a call signal (f) is transmitted to the terminal 7 on the basis of similar control.