One box solutions for CEMark testing including Surge, EFT and Dips and Interrupts. All units have software control and built-in single phase coupling. The NSG3040 and UCS500n5 have an external variac for performing the dips and interrupts test. The EMC Partner TRA3000 has this function built-in. The TRA3000 also has the common mode test per IEC 61000-4-16 built into the unit. The couplers and variacs are described in the Optional Equipment section below. http://www.transientspecialists.com