A programmable pulse generator capable of operating in several atrial and ventricular pacing modes having atrial and ventricular sense amplifiers and output circuits, programmable memory and clock controlled digital timing circuits and a depletable power source. End-of-life sensing circuits detect first...http://www.google.co.uk/patents/US4390020?utm_source=gb-gplus-sharePatent US4390020 - Implantable medical device and power source depletion control therefor
