Drive network for an ultrasonic probe

Claim 1

In a drive network for an ultrasonic probe, the drive network being of the type having a source operative to generate probe excitation signals at any one of a predetermined plurality of selectable frequencies in a range of frequencies, means coupled to the probe and operative to generate an electrical feedback signal representative of the motion thereof, a phase comparator having a first input terminal connected to the excitation signal and a second input terminal connected to the feedback signal, the phase comparator being operative to control the frequency of the excitation signal generated by the source in a manner such that, at the start-up of the network, when the feedback signal has a frequency greater than that of the excitation signal the source is caused to apply to the probe an excitation signal at a predetermined higher frequency, wherein the improvement comprises: a network responsive to a predetermined enable signal generated prior to the initial application to the probe of an excitation signal from the source at a first predetermined frequency for applying a pulse to the second input terminal of the phase comparator such that the frequency of the feedback signal applied to the phase comparator is greater than that of the excitation signal being applied to the phase comparator at the first input terminal thereof.