An object of this invention is to provide a key cylinder device which is simple in structure and is able to positively detect the presence or absence of the key. In a key cylinder device, a key cylinder body incorporates a rotor having a key inserting inlet, and a shutter made of a magnetic material...http://www.google.ca/patents/US5307658?utm_source=gb-gplus-sharePatent US5307658 - Key cylinder device
