saw tooth pulse which has a rapidly dropping trailing edge to effect deflection in the opposite direction with an overshoot at the maximum point of overshoot an alternating triggering voltage preferably in the form of a pulse sequence is applied to energize and maintain the transducer in resonance oscillation application_number US 23565381 A description in fig1 a saw tooth pulse 1 is illustrated having a rise 2 and a rapid drop 3 which is essential to the invention and moreover the shape of the time related slope of the rise is of subordinate significance as long as the deflection maximum is in fact attained at least to a large extent with the pulse 1 a practically complete mechanical deflection of the transducer is attained a curve 12 illustrates the mechanical deflection associated with the voltage rise 2 up to the value of the maximum deflection 14 the rapid voltage drop 3 leads to the return of the deflection along a path 13 with a following overshoot proceeding in the opposite direction up to the amplitude 15 the amplitude 15 calculated from the voltage drop 3 is attained after a time u03c4 2 where u03c4 is the above mentioned period of the self resonance of the transducer and that of.