To provide a positive indication that a medical lead terminal is properly secured within the longitudinal bore in the header of an implantable medical device there is provided a force sensor positioned within the device’s lead receiving bore and cooperating with the lock mechanism to provide an indication of the amount of force being exerted on the lead terminal to retain it in place. A wear leveling method for a non-volatile memory comprising a base area in which address mapping for data access is performed on a block basis includes selecting a unit having a high wear value from among a plurality of units included in each of a plurality of blocks of the base area and mapping the selected unit of the base area to a unit included in a log area. Thereby, a small operating current consumption can be achieved with a large supply voltage range. By contrast, the image is transmitted from the hand piece to an image presentation site by a camera assembly that is mounted to the hand piece and a relatively long electrical cable.