The Corrosion Service Portable Transformer Rectifier Unit (TRU) is one of the most essential tools in the cathodic protection technician’s tool box. The TRU allows a variety of surveys to be performed where they would not otherwise be possible by supplementing, mimicking, or replacing permanent cathodic protection installations. Common applications include coating holiday (DC voltage gradient) and current requirement surveys. The TRU provides high output voltage, allowing the generation of significant test currents even under high resistivity soil conditions. The unit is air-cooled with a continuously variable variac control and is conveniently fitted with an interrupter interface. Standard units are supplied with LED displays in a painted carbon steel cabinet, which is rugged enough to withstand demanding field conditions.