PURPOSE: To realize the subscriber terminal equipment in which a subscriber does not depend on the realization of the wait additional service in a busy state of an exchange and receives the service, by an equivalent function.

CONSTITUTION: When a subscriber terminal equipment F1 receives a registration request by a busy state wait command key F3, the information identifying a final called party saved by a redial function is registered in a relevant additional function program F9 and the program F9 is set to be started for a period of i-sec. The subscriber terminal equipment F1 gives a call request to an opposite party registered for the period of i-sec by its internal clock F14 and releases the registration automatically as to the wait registration in the relevant busy state when the call is received.