A demand cardiac pacer having provisions for determining power source life status both during normal heart operation and during heart stimulation by the pacer. An external magnetic pulse of relatively long duration induces a test mode in the circuit, the pacer reverting to the pacing mode immediately...http://www.google.com/patents/US4099530?utm_source=gb-gplus-sharePatent US4099530 - Cardiac pacer circuitry to facilitate testing of patient heart activity and pacer pulses
