Methods and apparatus are provided for electrically isolating an ambulatory medical device for infusing treatment materials into a patient when the medical device is connected to a peripheral device via an active communication cable. In one embodiment, the ambulatory medical device includes first circuitry controlling infusion of a medicament to the patient by a fluid conduit connectable to the patient and second circuitry controlling communications when an active communication cable is connected to the medical device. The first and second circuitry are electrically isolated using a pair of first and second isolation transceivers, where the first pair of isolation transceivers communicate a control signal and the second pair of isolation transceivers are giant magneto-resistive (GMR) transceivers that communicate at least one data signal.