Abstract: A cardiac pacemaker is provided which has combined defibrillation and electrosurgery protection. The pacemaker includes an implantable housing with a pacing circuit located within the housing and means for attaching a lead to the housing. A protection circuit is located between the pacing circuit and the attaching means. The protection circuit comprises a zener diode and a capacitor connected across the zener diode. The capacitor has a value to provide a relatively low impedance with respect to electrosurgery frequencies and a relatively high impedance with respect to cardiac myopotential frequencies.

Abstract: A telemetry system for transmitting digital data from an implanted pacer to an external programming/receiver unit includes a voltage-controlled pulse generator having an output period proportional to its input voltage magnitude. The external receiver unit includes a pulse period detector to generate a reconstructed analog signal whose amplitude is proportional to each pulse-to-pulse time interval from the pulse generator. The pulse generator requires only minimum width pulses and thus there is minimum system drain because the signal information is contained only in the pulse-to-pulse interval and not in the pulsewidth.