PURPOSE: To use one line for both a pushbutton telephone set and a rotary dial set by supervising the time of an input signal from the line so as to switch the connection of a pushbutton signal receiver and a voice recognition section based on the result of supervision.

CONSTITUTION: When an incoming call detection section 1 detects an incoming call, a main control section 7 activates a relay RL, a contact rl is closed and the sending of a voice synthesis tone for confirmation is instructed to a voice synthesis control section 2 through a signal line B. The synthesized voice is such as ' Please input an identification signal'#'.' and the main control section 7 activates a time supervisory section 6 through a signal line C. When a pushbutton input'#' is inputted from a signal line E during the supervision, an output of an output terminal C' is activated to reset the time supervisory section 6 thereby continuing the PB mode. On the other hand, if the output at the output terminal C' of a comparator 9 is not active within a prescribed time, the time supervisory section 6 sets a PBE/F 10, a signal at an output terminal D is made active to switch a multiplexer 8 to the position of the voice recognition section 4 thereby forming the voice recognition mode.