Intrusion alarm apparatus

摘要

This intrusion alarm apparatus is intended to be suspended from an inside doorknob and plugged into an A.C. power socket at the premises to be protected. A test switch and indicator lamp enable the user to determine (without triggering an alarm) whether the plug has the correct polarity in the power socket. The alarm signalling device in the apparatus or the indicator lamp is activated by the added capacitance of a person or an extraneous metal object touching the outside doorknob, depending upon whether the switch is in the "test" or "on" position.