To simplify the configuration of a harness and to improve ease of assembly in a vehicle assembling process.

Signals are given and received between a transmission device 11 mounted near a brake pedal 10 existing distant from the routing of a wire harness 20 routed inside a vehicle, and a neighbor unit 30 formed with a signal processing part 33 by means of optical communication using a light-intercepting circuit 31 and a light emitting circuit 14 of no-contact type, thereby eliminating the use of wiring to the transmission device and controlling the lighting of a stop lamp 24 based on the operable condition of the brake pedal discriminated by a signal processing part.