PURPOSE: To always necessitate only one piece of incoming call terminal even when the number of subscribers to be furnished with incoming call connection service while speaking is increased by selecting an incoming call device while speaking in vacant status, providing an amid-speaking incoming call controller to connect said device with a change-over means, and using the terminal that said device has on a line ling frame.
CONSTITUTION: If an subscriber CWSUB 11 capable of receiving incoming call connection service while speaking transmits, a transmission register OR 12 is connected and receives the telephone number of the opposite. Upon said reception of the telephone number, the OR 12 activates a connection marker CM13, and transmits the telephone number of the opposite and a subscriber location information. The CM 13 thereby activates a translator TLR 14 to transmits said telephone number and location information. Accordingly, the TLR 14 identifies a vacant out trunk information peritnent to a vacant out trunk OGT 15 and transmits it to the CM 13. The CM 13 connects the CWSUB 11 with the OGT 15 in accordance with the subscriber location information and the vacant out trunk information. Thereafter, the speaking of the subscriber 11 capable of receiving incoming call connection service while speaking entitled is started.