A device which allows radio frequency energy to pass in one direction with very little power loss, but blocks the flow of energy in the other direction by means of multiple wave-polarization or an integral dissipative load. It isolates frequency sensitive circuity from the effects of reflected radio frequency energy resulting from component mismatch. It usually has one or more ports terminated with coaxial connecto (s) and/or waveguide flange(s) ; or other electrical terminations. Isolators designed for internal use in waveguide runs may consist of rods, rings, chips, strips and the like and have no ports or terminations. See also diplexer; duplexer. Excludes circulator, radio frequency.