Importance

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Abstract

A generator of ultrasonic signals for a transducer which incorporates at least a phase lock loop feedback system for purposes of maintaining the output frequency between first and second voltage values also incorporates supervisory control circuitry for monitoring whether or not the generator and the transducer continue to operate in a resonant condition. In the event that the generator and transducer fail to stay in a resonant condition, the supervisory circuitry will super-impose a control voltage on the phase lock loop feedback path for the purpose of restoring the generator and the transducer to a resonant condition. To reduce the time to return to resonance, a representation of the last resonant frequency can be stored by the supervisory circuitry. When a loss of resonance is detected, the prestored value can be retrieved and superimposed on the phase lock loop feedback circuit for purposes of more quickly restoring the generator and the transducer to resonance.

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First Claim