| 摘要 |
PROBLEM TO BE SOLVED: To make code communications with amplitude modulation between a burglar prevention device and an electromagnetic connection transponder and to prevent unnecessary electromagnetic connection of the transponder such as a code tap or code interference caused by miscellaneous keys, etc., in the burglar prevention device capable of operating a car, etc., when the corde to be transferred is valid. SOLUTION: A transponder 2 is shielded with a conductor case 12 in a mode to selectively release only the side electromagnetically connected to an antenna coil 4 of the transponder incorporated in a handle part of a key 1, and directivity is kept in the direction of the electromagnetic connection of the transponder 2. By such construction of the key 1, the transponder 2 is properly electromagnetically connected to the magnetic field BD applied from the antenna coil 4 side, and the magnetic field BD' applied from another direction is so favorably prevented that unnecessary electromagnetic connection is made. |
