Comes with On/Off switch and wall power supply. The wall adapter can be cut at the wall end, and this puppy can be use in a 12v Vehicle !Compact SWR & Power Meter with Antenna MatcherMeasures Up to 100 Watts Single WindowMounting Bracket Included Power/SWR Meter and Antenna Matcher Rated 100wattsSpecifications: 27 MHZ Band SWR - 1:1 to 3:1 RF power - 0-10 watts - 0-100 watts Impedance - 52ohms Accuracy - SWR 5% - RF power 10% Connectors - SO239 Can be used inline for constant reading