Disclosed is a pacemaker having an output circuit which is set to a high impedance when the potential of the input signal transmitted through the input-output terminal is within a predetermined range, and is set to a low impedance when the potential of the signal is outside of the range. Therefore, the...http://www.google.co.uk/patents/US5285780?utm_source=gb-gplus-sharePatent US5285780 - Pacemaker with improved pulse detection
