A speed regulator digital speed controller for rotating machinery is comprised of a single-chip microcontroller operating in conjunction with a multiple counter/time peripheral, and is programmed in a high level language. Pulses are generated by a digital speed sensor at a rate too low to give the required...http://www.google.se/patents/US4845608?utm_source=gb-gplus-sharePatent US4845608 - Digital speed controller using a single-chip microcontroller
