Abstract: An implantable programmable pacer is disclosed which incorporates a program logic system for receiving magnetic signals from a simple magnet source applied external to the patient, and for translating the simple magnetic signals into logic signals for re-programming selected pacer parameters. The circuitry of the programming system is adapted to react to predetermined timed sequences of application of the external magnetic signal, which timed sequences are correlated with successive intervals of the pacer stimulus generator. The programming system is adapted to interpret predetermined patterns of external application of a magnetic field as instructions for re-programming respective operating parameters.