A controller for driving an ultrasonic transducer is disclosed and includes a processor, responsive to a feedback signal, for generating control signals to an output driver which is responsive to the control signals, to cause the ultrasonic transducer to generate ultrasound having a power level corresponding...http://www.google.se/patents/US6261249?utm_source=gb-gplus-sharePatent US6261249 - Ultrasonic treatment controller including gel sensing circuit
