this example that commands every component part of the system in accordance with a program a control circuit that controls the voltage to be applied to piezoelectric crystal 8 in accordance with an instruction from the cpu timer 4 i8253 is used in this example that controls the pulse time in accordance with an instruction from the cpu and a driver circuit for piezoelectric crystal 8 firstly the controls of the preceding pulse voltage and of the main pulse voltage will be explained the cpu instructs latches 1 and 2 on the voltage to be applied to piezoelectric crystal 8 and the timing of the voltage application is also fed from the cpu to the cs of each of latches 1 and 2 latches 1 and 2 each therefore puts out a signal telling when what voltage should be applied to piezoelectric crystal 8 the output from each of the latches is a digital signal the signals are converted into analog signals by d a transducer dac and the analog signals are amplified by amplifiers amp and then fed to the collectors of transistors tr 7 and tr 8 respectively the transistor tr 7 is one that is provided for making on off control to determine whether or not to apply the advance pulse voltage to piezo electric crystal 8 if this transistor tr 7 is turned on the voltage applied to the collector i e the peceding pulse voltage controlled in accordance with.