Phase Detectors/Shifters are devices that measure the phase difference between two signals. This can be used for a variety of purposes such as demodulation and controlling the frequency of an oscillator. Commonly used phase detectors use switching characteristics and can be used to discriminate between multiple waveforms. A phase detector/shifter can be used to determine the phase difference between two waveforms by looking at the differences in their waveforms. This can be used for frequency and phase locked loop systems. In these systems, a phase detector/shifter will be used to compare the phase and frequency of one waveform to that of a reference waveform and then adjust an oscillator to align the two waveforms.