PURPOSE: To simplify the constitution by applying input/output control of a body electronics with a conventional communication equipment and using the communication equipment used together with a microcomputer for the control of an intelligent device.

CONSTITUTION: Simplex stations 10, 11 are communication equipments and duplex stations 20, 21 are also communication equipments. The simplex stations 10, 11 and the duplex stations 20, 21 are connected by a communication line 5 of balanced transmission system. Body electronics 40, 41 such as switches and lamps are connected respectively to the simplex stations 10, 11. Moreover, the duplex stations 20, 21 are used together with microcomputers 30, 31 and the duplex stations 20, 21 and the microcomputers 30, 31 constitute an interface section of control sections 42, 43 of an intelligent device. Interface sections 60, 61 constitute the interface with the body electronics 40, 41.