PURPOSE: To simplify the control by sending a strobe signal at the end of one preceding transmission burst and sending a frequency division data signal just after the transmission of a strobe signal sent after the end of 2-preceding transmission burst, thereby to controlling the operating timing.

CONSTITUTION: The strobe 103B of a strobe signal to set the frequency f3 of a transmission burst 103 is sent at a point of time t2 after the end of one preceding transmission burst 102. Moreover, the frequency division data 103A of a frequency division data signal is sent just after the transmission of the strobe 102B sent at a point of time t1 after the end of two-preceding transmission burst 101. Thus, a control circuit 40 applies the control such that the strobe signal is sent in precedence of the frequency division data signal in matching with the operating timing when a switch 20 interrupting the transmission signal is interrupted. Since the operating timing is decided independently of the difference of the locking time due to the kind and the frequency, etc., of the frequency synthesizer 30, the control is simplified.