An EKG signal processing apparatus comprising an input to which the EKG signal may be applied, an output at which the processed EKG signal is to appear, a resistor and a normally conductive signal switch connected in series between one terminal of said input and one terminal of said output, a capacitor...http://www.google.de/patents/US4574813?utm_source=gb-gplus-sharePatent US4574813 - Pace pulse signal conditioning circuit
