PURPOSE: To attain ease of extension and external line talking by an extension telephone set near a moving location even when a called party moves to any location in a system by adding a position recognition means and a control means to confirm the location of the called party to a private branch of telephone exchange.

CONSTITUTION: When an external telephone call comes, the operator confirms a called party and adds an identifier assigned to the called party and a call signal is sent via an exchange 1. Then a 1st position recognition means 5 arranged to each of plural extension telephone sets 2 requests an acknowledge signal for confirming the position of the 2nd position recognition means 6 corresponding to the called party. The acknowledge signal from the 2nd position recognition means 6 is received by plural 1st position recognition means 5 and a control means 4 detects a 1st position recognition means 5 closest to the called party based on the reception signal and connects the external telephone call to the extension telephone set 2 corresponding to the 1st position recognition means 5. Thus, the called party replies the phone call regardless of the location of the called party.