An intrusion alarm system of a variety utilizing an inertially responsive sensor preferably present as a pendulum actuated reed switch. Logic circuits provided within the system provide, in one embodiment, an efficient pulsating alarm at dual frequencies optimized for human recognition. In another arrangement,...http://www.google.fr/patents/US4122437?utm_source=gb-gplus-shareBrevet US4122437 - Intrusion alarm control system
