MEDICAL SYSTEM COMPRISING AN IMPLANTED INTERNAL UNIT, AN EXTERNAL UNIT, AND A METHOD OF INITIATING OPERATION OF EXTERNAL UNIT

A method of initiating operation of an external unit for a medical system further comprising an internal unit implanted into a body of a patient; a transformer core arranged under the skin of the patient; and internal cabling connecting the internal unit and the transformer core, the internal cabling comprising an internal winding around the transformer core, wherein the external unit comprises external cabling including an external winding around the transformer core to allow supply of power from the external unit to the internal unit via the transformer core, the method comprising the steps of: evaluating, by the external unit, a signal indicative of a magnetic flux in the transformer core; when the signal indicates that the magnetic flux in the transformer core is below a predefined threshold flux, providing power to the internal unit by the external unit via the transformer core.