An access system for controlling access of a user to one of several unique operative modes of an electronic device used to communicate with an implantable medical device. The access system includes a portable keycard, which is held by a user. The keycard has embedded magnets arranged in a unique predetermined pattern. The electronic device has a housing that provides a slot and a channel for receiving the keycard by the user. A sensing circuit and a processing circuit are both provided. The sensing circuit includes Hall-effect transducers positioned next to the channel so that upon inserted of the keycard, certain ones of these Hall-effect transducers will reside adjacent a magnet, depending on the particular unique pattern. A magnet positioned adjacent a Hall-effect transducer will cause the transducer to send an output signal to the processor indicating the presence of a magnet at the location of the Hall-effect transducer. The Hall-effect transducers collectively generate an electronic pattern representing the particular identity of the keycard. The processor compares this electronic pattern with one of several stored in electronic memory and provides selective access to the device in response to successfully identifying a match. A doctor, a technician, a salesperson and a factory assembly worker are examples of users of this system and each will be granted predetermined access rights to operate the device. Additional Hall-effect transducers may be provided to help detect the intrusion of magnetic fields produced from magnets not located with the keycard. The process will deny any access to the device should any such remove magnetic fields be detected.