| 摘要 |
PROBLEM TO BE SOLVED: To attain the rapid improvement of secret talk performance not accomapnied by complication of hardware constitution and a rise of manufactur ing cost, and to flexibly cope with the ciphering method for a transmission signal and the change of the format of cipher code, etc. SOLUTION: In the transmitter-receiver 2 incorporated into the key grip of an ignition key, a microcomputer 3 is switched to its active state by the output of a power source circuit 12 smoothing/rectifying the carrier wave signal from the transmission-reception ECU on the side of an automobile in a state that a resonance circuit part 7 receives the carrier wave signal. A detection circuit 13 discriminates the question signal imparted with the carrier wave signal through the resonance circuit part 7 and imparts the signal to the microcomputer 3. When the microcomputer 3 switched to the active state receives the question signal, the microcomputer 3 perform the control of returning the response signal of a ciphered state to the side of a transmission-reception ECU by preparing the cipher code by the function calculation based on the discrimination code, the code for calculation and the function expression in an EEPROM 4 and performing the on/off control of the FET 6a within a modulation circuit 6 by the mode corresponding to the cipher code. |
