An encoder circuit particularly suited for a switched reluctance (SR) electric motor includes a single switch and a plurality of encoder windings. Each one of the plurality of encoder windings is connected to the switch. When closed, the switch initiates current flow through the windings....http://www.google.com/patents/US5783940?utm_source=gb-gplus-sharePatent US5783940 - Encoder circuit for determining the position of a rotor of a multiphase motor 
