SWR meters are used to measure the standing wave ratio (SWR) in radio equipment. They are sometimes called VSWR meters, a reference to voltage standing wave ratio (VSWR). SWR is the ratio of the amplitude of a partial standing-wave at maximum amplitude to the amplitude at an adjacent node. In telecommunications applications, standing wave ratio is a measure of the quality of the match between the antenna and the receiving system. VSWR is the ratio of the maximum voltage to the minimum voltage on an electrical transmission line. In other words, it is a measure of the impedance mismatch between a transmission line and load.