PURPOSE: To prevent the interference and the degradation in reception sensitivity by providing a signal line through which a carrier signal is supplied to the modulating circuit of a transmission circuit, a frequency dividing circuit, and a circuit which inhibits supply of the carrier signal in the reception slot period.

CONSTITUTION: In the transmission slot period, a switch circuit 55 is turned on by a control signal Sw, and a voltage Vcc of a terminal 54 is supplied to a frequency dividing circuit 52, and a carrier signal Sc is taken out from the circuit 52. In the reception slot period, the circuit 55 is turned off by the control signal Sw, and the circuit 52 itself is not operated because the operating voltage Vcc is not supplied to the circuit 54. Since the carrier signal Sc is not outputted from the circuit 52 though an oscillation signal Sn from an oscillating circuit 51 is supplied to the circuit 52, the carrier signal Sc or a transmission signal St is not leaked to a reception circuit 20, and the interference and the degradation in reception sensitivity are prevented.