In-vehicle device control system

An in-vehicle device control system comprising:

• a portable device;
• and
• a vehicle-side unit mounted on a vehicle for performing a checkup about the portable device by mutual communication, in which the vehicle-side unit transmits a request signal and the portable device returns a response signal in response to the request signal of the vehicle-side unit, thereby to control an in-vehicle device based on a check result, the vehicle-side unit switching a communication frequency to perform the mutual communication and the checkup again when the check result indicates an unsuccessful checkup,
• wherein the portable device includes:
• a portable device communication section for receiving the request signal transmitted from the vehicle-side unit and returning the response signal as the mutual communication with the vehicle-side unit, the response signal including an ID code and transmitted at a communication frequency designated by the vehicle-side unit,
• wherein the vehicle-side unit includes:
• a detection section for detecting an operation of a user, by which the checkup is started;
• a frequency setting section for setting the communication frequency to be designated to the portable device;
• a vehicle-side communication section for transmitting the request signal to the portable device and receiving the response signal as the mutual communication with the portable device, the vehicle-side communication section transmitting to the portable device frequency information indicating the communication frequency set by the frequency setting section;
• a checkup section for checking up the ID code and a registration code pre-registered, the ID code being included in the response signal transmitted from the portable device and received from by the vehicle-side communication section;
• a storing section for storing the communication frequency, which is used when the check result indicates a successful checkup;
• and
• an estimation section for estimating a change in a radio wave environment, in which the vehicle and the portable device are located, after the successful checkup by the checkup section,
• wherein the frequency setting section is configured to switch over the communication frequency to be designated when the checkup result indicates the unsuccessful checkup, and
• wherein the frequency setting section is configured to fix a communication frequency to the communication frequency stored in the storing section in response to the successful checkup, when no change in the radio wave environment is estimated.