In applications requiring sinusoidal AC waveforms, magnitude, frequency, and phase should all be controlled. Time measurements are easier to interpret pulses and complex waveforms. DigiPro Doubledraw allows the user to create an oscillator by blending two different waveforms. The spectral density of these switching waveforms has energy concentrated at relatively high frequencies. SSB techniques can also be adapted to frequency-shift and frequency-invert baseband waveforms (voice inversion). This is particularly useful in power electronics, where non-sinusoidal waveforms are common. Wavetable synthesis is a sound synthesis technique used to create periodic waveforms. Note that the specification mentions only sinusoid waveforms. The sounds include sampled attack transients, loops, sustained waveforms without attack transients, and percussive samples. Digital instruments exist that directly measure the time lag between voltage and current waveforms. A 'non-inverting' amplifier maintains the phase of the input signal waveforms. The images may represent electrical waveforms (oscilloscope), pictures (television, computer monitor), radar targets or others. Higher precision can be achieved with pulsed waveforms. Synthesizers and modern keyboards can generate sounds with many complicated waveforms. DigiPro-Wave offers 32 waveforms, with interpolation between adjacent waveforms.