| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a communication device, a portable machine and a communication system capable of performing suitable communication in response to a communication environment. <P>SOLUTION: When performing bidirectional communication between a door unlocking control device 3 and the portable machine 2, a plurality of index signals mutually different in a voltage level are generated by a microcomputer 24. The plurality of index signals are added to a request signal and transmitted by a transmission circuit 22. Then, the voltage level when transmitting an ID code signal, is determined by a microcomputer 14 with the plurality index signals mutually different in the voltage level transmitted by being added to the request signal in this way as an index. The ID code signal of the predetermined voltage level is generated by the microcomputer 14. The ID code signal is transmitted by a transmission circuit 15. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
