PURPOSE: To attain the selection of a caller independently of a calling system of a telephone set, by transmitting a decimal number by one digit each by a voice synthesis signal after transmitting the absence of an incoming call to a caller, and confirming that a number responded "Yes" by the caller is coincident with a special number.

CONSTITUTION: A call signal is detected at a call signal detecting circuit 2 at the incoming of a main trunk 1 and transmitted to a sequence control section 3. The control section 3 activates an off-hook circuit 4 to make calling state and responds to the incoming call for attaining the calling state. The control section activates a message transmitting circuit 5, which transmits a message representing the absence of a called party and collating number succeedingly such as "0,1∼8,7" in a prescribed pause for each by means of a voice synthesis signal for the desired number of times. When the caller responds "Yes" to a voice number, it is received at a voice signal receiving circuit 6, which converts the signal into a digital signal. This signal is fetched to the control section 3 and only when the responded number is collated with a stored number and coincident with each other, a calling level 8 is operated to communicate with the caller through a telephone line 9.