PURPOSE: To reset a mobile set main body and a telephone set simultaneously without increasing the number of signal lines by operating a reset circuit of a telephone set from a reset circuit of the mobile set main body with a signal having a frequency distincted from a frequency used for data transmission/ reception.

CONSTITUTION: An oscillator 4 having an oscillation frequency distinguished from a frequency used for data transmission/reception through a signal line 9 between the mobile set main body 1 and the telephone set 2 is provided to the mobile set main body 1. In the operation of the reset circuit 3 of the mobile set main body 1, when the oscillated frequency of the oscillator 4 sent via the signal line 9 is detected, a reset circuit 8 of the telephone set 2 is activated. A detection circuit provided in parallel with a circuit connected to the signal line 9 is provided to the telephone set 2. Thus, the mobile set main body 1 and the telephone set 2 are set initially at the same time. Since the frequency of the oscillator 4 is set to the frequency distinguished from the frequency used for transmission/reception of data, the telephone set 2 is not reset in sending the data from the mobile set main body 1 to the telephone set 2.