| 摘要 |
<p>PROBLEM TO BE SOLVED: To shorten the time of communication between question equipment and answer equipment. SOLUTION: A transponder 2 is built in the key grip of ignition key 1 and activated by generating operating power by smoothing/rectifying a carrier wave signal from a transmission/reception ECU 10 on the side of automobile in the state of receiving that carrier signal. The transmission/reception ECU 10 transmits a question signal by reducing the signal level of carrier wave signal into prescribed level at prescribed timing. The transponder 2 judges the question signal based on the timing to reduce the signal level of carrier wave signal and returns an answer signal in response to that question signal. At such a time, since the level reduction of carrier wave signal is set so that the transponder 2 can be turned into level for transmitting the answer signal by impedance conversion to the carrier wave signal, the signals can be simultaneously exchanged between the transmission/reception ECU 10 and the transponder 2.</p> |
