To improve the convenience by calling a telephone set, which corresponds to a received extension number, out of plural telephone sets registered correspondingly to extension numbers.

Plural telephone sets 116a to 116c are registered in a RAM 103 correspondingly to extension numbers by an operation part 104, and a call signal detection circuit 111 detects a call signal from a direct inward dialing line 110. When the extension number of a DTMF is received, the telephone set corresponding to this extension number is retrieved from the RAM 103, and the call signal is sent to only this telephone set from a call signal generation circuit 114.