PURPOSE: To eliminate the need for the connection change of a transmitter- receiver and the setting change of the address inherent in a receiver by providing an address part with a fixed value and a variable address part in the transmission data of the transmitter-receiver connected in series.

CONSTITUTION: The transmitter 1 is connected to plural receivers 2 and 3 in series, and the address part 6 with the inherent value and the variable address part 7 are provided in data transmitted from the transmitter 1 to a desired receiver. The address parts 6 and 7 in a reception frame are compared with a comparator 12, a data read circuit 14 reads a data part 8 in the reception frame when the address part 6 with the inherent value coincides with the variable address part 7. Meanwhile, when noncoincidence is obtained, the variable address part 7 is added at an adder circuit 13, and an addition result is set at the variable address part 10, then, the data is transmitted to the receiver. In such a manner, it is possible to eliminate the need for the connection change of the transmitter-receiver and the setting change of the address of the value inherent in the receiver.