IN-VEHICLE DEVICE, RECORDING MEDIUM, AND KEYLESS ENTRY SYSTEM

An in-vehicle device includes transmitting antennas, an in-vehicle device transmitter configured to transmit request signals from the respective transmitting antennas, an in-vehicle device receiver configured to receive, from a portable device, an answer signal that includes received signal strengths of the respective request signals, and an in-vehicle device controller configured to calculate a distance from the portable device to each of a plurality of areas, based on both the received signal strengths of the respective request signals included in the answer signal and reference values for the request signals, and to identify an area to which the portable device belongs based on the distance. In a case where there is a request signal whose received signal strength is not included in the answer signal, the in-vehicle device controller calculates the distance by utilizing a corresponding reference value for the request signal as the received signal strength of the request signal.