| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent a product from erroneously operating a burglar prevention gate by making respective responders switch response signals from a first mode at a first output level to a second mode at a second low output level in response to mode switching signals from an interrogator. SOLUTION: A code generator 42 generates a coded signal for indicating information stored in the responder and a modulator 43 superimposes the coded signal on a carrier received from an antenna, modulates it and supplies the modulated carrier through an attenuator 44 to the antenna 40 so as to transmit it as the response signal. A gap detection logic circuit 45 detects both ACK signals and SWITCH signals. A mode control bit 47 controls the attenuator 44, and when the bit is set, the attenuator lowers the output level of the response signals from a normal level to a low level. The low output level is detected in a range equal to or less than 10cm.</p> |
