Patent ID: 7429922

Claim:
A system that allows two-way communication between a portable unit and an in-vehicle unit in a manner that the portable unit transmits a response signal including an ID code in response to a request signal transmitted from the in-vehicle unit, so that the in-vehicle unit receives the response signal from the portable unit, performs a comparison between the ID code included in the response signal and a pre-registered code, and controls vehicle equipment in accordance with a comparison result, wherein the in-vehicle unit comprises: transmitter means that transmits the request signal in a vehicle compartment; and receiver means that receives the response signal from the portable unit, characterized by further comprising: output varying means for varying an output level of the request signal transmitted from the transmitter means; specifying means for specifying a location of the portable unit in the compartment based on changes in receptions of the response signal transmitted in response to the request signal of varying output level; and notifying means for notifying the location of the portable unit specified by the specifying means.