To improve the convenience, to reduce the power consumption, and to enhance the crime preventive performance of a control device which carries out radio communication of signals inclusive of collating information between a main machine and a portable machine, and carries out some type of control by the main machine which has confirmed and verified that the portable machine is the one concerned.

The portable machine 10 is switched from a sleeping state (reply disabled state) to an activated state (replay enabled state) by the operation of an operating section (unlocking switch 12 etc.). When the portable machine 10 receives a request signal which is intermittently transmitted by the main machine 20, the portable machine 10 automatically transmits an answer signal inclusive of an identification code. Then, the main machine 20 which has received the answer signal confirms and verifies the identification code, and then the main machine 20 carries out some kind of control.