PURPOSE: To surely perform call back redialing from an incoming call interphone terminal to an outgoing call interphone terminal by storing a call originating number in the call originating memory of an interphone exchange, and storing the call originating number read out in a dial buffer transiently.

CONSTITUTION: Each of interphone terminals TE1-TE5 on which a microphone 1, a speaker 2, ten keys 3, a redial button AK and a call back dial button BK, etc., are packaged is connected to the interphone exchange EQ1. The call originating number is stored in the call originating memory BM of the RAM 11 of the exchange EQ1, and the call originating number read out from the memory BM corresponding to the operation of the button BK by the incoming call interphone terminal 11 is stored in the dial buffer BM transiently. The call back redialing from the incoming call interphone terminal to the outgoing call interphone terminal can be surely performed based on a content stored in the memory.