Abstract: As the battery of a heart pacemaker is discharged, its internal resistance rises, as a result of which the amplitude of the stimulation pulses decreases. In order to still be able to generate stimulation pulses with an amplitude which lies above the threshold of the heart even given a battery which has already been largely discharged, it is inventively provided that the discharge of the output capacitor can only be triggered given attainment of a specific minimum voltage (V.sub.min) at said output capacitor. That can be advantageously executed with the assistance of a comparator which compares the voltage at the capacitor to a comparison voltage (V.sub.min) and which inhibits the actuation of a switch via a NOR gate until matching has been achieved. The base frequency of the heart pacemaker and the pulse width can be fixed by two monostable flip-flops.

Abstract: The exemplary embodiment comprises a pulse generator which is controlled by means of a parent frequency generator with a prescribable parent frequency, and a control circuit with setting generator for setting desired pulse repetition rates of the pulse generator for the heart pacemaker pulses as a function of the setting value of the setting generator. The purpose of the disclosure is to develop such a heart pacemaker with simple technical means to such end that a preselection of the pulse repetition rate of the heart pacemaker is possible directly in pulse per minute. This goal is inventively achieved in that the parent frequency signal (f.sub.o) of the parent frequency generator is supplied to a binary frequency multiplier together with a binary multiplication signal (n) of a multiplication signal generator which is adjustable as a function of a pulse per minute setting value (F) of a pulse per minute setting generator, said binary frequency multiplier converting the parent frequency (f.sub.