In telecommunications, Standing Wave Ratio (SWR) is the ratio of the amplitude of a partial standing wave, at an antinode (maximum) to the amplitude at an adjacent node (minimum), in an electrical transmission line. The SWR is usually defined as a voltage ratio called the VSWR, (sometimes pronounced "viswar), for voltage standing wave ratio. For example, the VSWR value 1.2:1 denotes a maximum standing wave amplitude that is 1.2 times greater than the minimum standing wave value. It is also possible to define the SWR in terms of current, resulting in the ISWR, which has the same numerical value. The power standing wave ratio (PSWR) is defined as the square of the VSWR. SWR is used as an efficiency measure for transmission lines, electrical cables that conduct radio frequency radio signals, used for purposes such as connecting radio transmitters and receivers with their antennas.