PURPOSE: To improve the operability of a receiver by reducing the size of the receiver and to reduce the cost of a telephone system as much as possible, in a telephone system provided with a hand-free function.

CONSTITUTION: A handset 10 is connected to a radio equipment 5 through an incoming sound signal line 17 and an outgoing sound signal line 18, and a cradle side light receiving part 14 receives an optical information signal from the handset 10, makes photoelectric conversion and outputs an electric signal to a speaker 7. When, hearing calling sound, a vehicle driver brings the handset 10 into a communicatable state and sets a communication mode to handset communication (hand-free communication) with a communication mode selection part 19, a CPU 2 outputs a switching signal to a sound switching circuit and switches the incoming sound signal line 17 to the side of an internal microphone 4 (hand-free circuit 6) and the outgoing sound signal line 18 to the side of a receiver 3 (hand-free circuit 6) to make possible the communication with the handset 10.