Voltage controlled oscillator 40 has an oscillation stoppage cancelling circuit 46 and a current/frequency converter circuit 44 which is a ring oscillator made by connecting inverters forming 3 stages like a ring. Oscillation stoppage canceling circuit 46 stops and releases oscillation of the ring oscillator...http://www.google.co.uk/patents/US5285483?utm_source=gb-gplus-sharePatent US5285483 - Phase synchronization circuit
