Anti-theft device using the same and method of reading regular ID code

摘要

PROBLEM TO BE SOLVED: To quickly and reliably collate both even when plural keys are installed in a key holder by transmitting a password demand signal when an ID code cannot be rightly read by a controller unit, and reading the ID code sent back to it. SOLUTION: An ID code demand signal is transmitted to plural transponders 75a, 76a in the first place. Next, when an ID code sent back to it from the transponders 75a, 76a cannot be rightly read by a controller unit, the password demand signal is transmitted from a vehicular coil 71, and an ID code sent back to it is read from a memory 80. Next, whether or not the received ID code is normal is judged, and when it cannot be judged, the password demand signal is transmitted until a normal ID code is authorized, and ID code sent back to it is read. The ID code can be reliably read in a short time by this operation.