Subcutaneous Implantable cardioverter-defibrillators are disclosed that are entirely implantable subcutaneously with minimal surgical intrusion into the body of the patient and provide distributed cardioversion-defibrillation sense and stimulation electrodes for delivery of cardioversion-defibrillation shock and pacing therapies across the heart when necessary. A planar light guide disposed substantially parallel to the front surface, has a periphery at least coextensive with the viewing area. The communication device is operable to determine a default mix signal gain, a downlink gain adjustment and a calibration gain based on the determined audio requirements, and to calculate the total gain for the downlink processing path based on the determined default mix signal gain, the downlink gain adjustment and the calibration gain. In response to the entry being present, the completion unit stores the received instruction group in a second location in the entry to form a stored instruction group.