BEI introduced a multi turn absolute encoder, the HMT25, with electronic reset capability. Unlike manual resets (buttons or switches) an electronic reset can use system software for initialization. This greatly improves machine set-up time, especially in systems with space constraints. Sending a timed pulse through the reset pin, the encoder value gets set to "zero" through a non-volatile internal memory. Since the encoder uses a geared multi-turn code wheel system, instead of a battery-dependant electronic turns counter, the physical position at any time is precisely determined even in prolonged power down situations.

More information:
BEI Technologies, (PDF Document)