The K34-59991A Phase Comaprator compares the phase relationship of two signals. It displays the phase on a center-reading meter on the front panel, as well as outputs a voltage on a rear-panel BNC connector representing the relative phase. It has a a frequency range of 100kHz to 10MHz and an input voltage range of 100mV RMS to 10V RMS.

Its output can be used with a strip chart recorder, digitizer, DVM, etc.