Vehicle tax system has vehicle mounted device having control circuit that performs preset operation if specific code of return signal matches with main code, and return signal and normal signal of portable device corresponds to each other

摘要

A portable device (3) carried by user of vehicle has control circuit (32) and clock generating circuit (35). The control circuit detects whether frequency of clocks of vehicle mounted device (2) and portable device corresponds to each other and sends return signal indicating specific code to vehicle mounted device. The vehicle mounted device has control circuit (4) that performs a predesignated operation if specific code of return signal matches with stored main code, and return signal and normal signal of portable device corresponds to each other.