A heart pacer providing heart stimulating electrical impulses in the absence of naturally occurring heartbeats, including two electrical impulse generating time bases each capable of emitting heartbeat stimulating impulses. A sensed signal, accepted against criteria preceding it in time, as a valid heartbeat...http://www.google.fr/patents/US3972334?utm_source=gb-gplus-shareBrevet US3972334 - Demand heart pacer with dual time bases
