The HP 70138A Vector Voltmeter is a two-channel measuring receiver that measures the magnitude of the signals at its inputs and the phase difference between them. Depending on the application and measurement configuration, the results of these basic measurements can be presented in various different ways - as voltage and phase angle, power in a 50 or 75 ohm system, magnitude ratio or reflection coefficient, for example. The results displayed for reflection measurements assume that the A input is the incident signal and the B input is the reflected signal. An appropriate signal separation device such as a bridge or directional coupler is assumed.