PURPOSE: To simplify a system constitution and to reduce the relative error of information, by using a single transmitter/receiver for transmission of signals in two circuits.

CONSTITUTION: A transmitter turns the output of an oscillating part 6 into a carrier wave electric power after modulating the output by a data signal through a modulating circuit 7. At the same time, the output of a local oscillating part 1 which is double as much as an intermediate frequency is mixed with the carrier wave at a mixing part 2 to generate a side band of the sum or difference of both frequencies. This output is modulated with a strobe signal through a modulating circuit 3 and radiated through a filter 5 to eliminate the disturbance of the carrier wave. In a receiver, the side band of modulation of the strobe signal through a filter 9 for the supplied carrier wave and side band are selected. Then the carrier wave of data signal modulation is selected through a filter 18 and converted into an intermediate frequency at mixing parts 10 and 19. This intermediate frequency signal is applied with voltage amplification through a distributor 16 which transmits selectively the intermediate frequency signal by an FF circuit control signal and then is detected through a detection circuit 12. Then the strobe and serial data signals are delivered.