To improve operability of the call operation of a user by discriminating a selection signal transmitted at the time of the call operation from an analog unit, starting the timer of a timer value which corresponds to the number of dialing digits, which corresponds to the number of the selected signals, and executing cell operation, based on information on the respective digits of the selection signals inputted until then.

When an analog port control part 9 detects off-hook state of a telephone set TE, it notifies of this to a main control part 1, and dial tone is transmitted to TE. When a user dial-operates a destination telephone number, the control part 9 notifies the main control part 1 of inputted dial information, sets a prescribed timer value in an input decision timer and starts the timer. When time out made, the main control part 1 informs a Dch control part 6 of all digit information for the input dial information stored in a storage part 4. The Dch control part 6 generates a call setting message based on dial information and starts a call operation.