| 摘要 |
PROBLEM TO BE SOLVED: To realize a substantial improvement of the secrete communication performance without deterioration of communication performance, and also prevent a transponder to be large sized and the cost to be increased. SOLUTION: A microcomputer 3 is turned to an active state when an output voltage of a power supply circuit 12 which rectifying and smoothing a carrier signal transmitted with a standard time signal and a query signal from a transmitting/receiving ECU of a vehicle side becomes over a predetermined level, in a transmitting and receiving unit 2 incorporated into a key grip of an ignition key. The microcomputer 3 turned to the active state measures a time width of the standard time signal received using a clock signal of a CR oscillation circuit 14, and computes a ratio of the time width measured and a standard time value stored in an EEPROM 4 as a correction coefficient, and at the time of a decoding operation of a query, the decoding operation is performed while correcting a time information in a time series pulse signals comprising the query signal using above mentioned correction coefficient. |
