Abstract

There is disclosed herein a programmable cardiac pacemaker pulse generator utilizing digital circuitry for controlling the provision of cardiac stimulating pulses. The pulse generator is capable of having the rate, the pulse width, the pulse amplitude, the refractory period, the sensitivity and the mode of operation programmed. In addition, the pulse generator can have the output inhibited and can respond to programming signals causing a threshold margin test to be performed, accomplished by threshold safety margin means responsive to a programmed test signal for causing a series of stimulating pulses to be provided a rate different than the previously programmed rate with at least one of the stimulating signals having its energy reduced a predetermined amount. Capture at the reduced energy can be monitored by external equipment.