Abstract: An oscillator circuit for use with a supply line and a line at a reference potential includes a crystal and a switching stage, the switching stage being closeable to connect the crystal to the supply line via one terminal of the crystal. The other terminal of the crystal is connected to the line at reference potential. Closing of the switching stage is controlled by a drive unit, which has an input to which the output of the switching stage is fed back. The drive circuit causes the switching stage to be briefly closed during a half period of the oscillation. If the oscillator circuit is manufactured as an integrated circuit, only one terminal pin is required for connection to the crystal, thereby saving space.

Abstract: To make it possible to suppress spurious signals of any type without having a negative effect on the stimulation or detection characteristics of a cardiac pacemaker, a signal processing unit is provided which prevents control signals from being applied to the device for controlling the heart stimulation pulses when signals from the two unipolar pacemaker electrodes are received at substantially the same time.