The pulses coincide with peak or near peak amplitude of an accompanying sinusoidal voltage waveform. In either case, the output waveforms are phase shifted to obtain a 12-step waveform. Modulation can be used to represent a digital message as an analog waveform. This vibration results in a periodic acoustic waveform comprising a fundamental frequency and its harmonics. The output voltage has a shape that approximates a square waveform. A transformer converts alternating current at one voltage to the same waveform at another voltage. Modulators act to provide the waveform of the RF-pulse. Because only one half of the input waveform reaches the output, mean voltage is lower. The average value of a repetitive pulse waveform depends on the area under the waveform. The total time period of one cycle of output waveform is constant. The current is input as an alternating current (AC) waveform. This because it is an integration of the input waveform over interval ts. There are two methods of receiving the ultrasound waveform&colon; reflection and attenuation. Current source inverters convert DC current into an AC current waveform. Audio mixing is supported by curves, visualised as line segments drawn over an audio waveform.