Particular key identification for motor vehicle security - analysing acoustic spectrum obtd. from microphone exposed to sounds of key insertion and rotation in ignition lock

摘要

The key when inserted into or rotated within the lock generates acoustic noise whose frequency spectrum contains components characteristic of the eigen frequencies of the key and lock. Comparison of the spectrum with one measured and recorded for an authentic key enables any attempt at operation of the lock with a spurious key to be forestalled. A microphone or piezoelectric element is coupled rigidly to the ignition lock, and its output is amplified, digitised and stored for authentication. ADVANTAGE - key is positively identified from frequency spectrum of noise which it generates, so that engine-starting with false key is excluded, practically without modification of ignition lock.