A counter electromotive force due to electromagnetic induction is generated on interruption of a current if an actuator 10 is in a normal state. An output signal generated by the counter electromotive force and a pulse signal which is generated from the fall of an input signal applied to the electronic...http://www.google.com/patents/US5404262?utm_source=gb-gplus-sharePatent US5404262 - Apparatus for driving electromagnetic actuator
