Tester allows to test your HDMI cables even if they are installed in the wall. Sold as a transmitter and receiver pair. The receiver unit has 9 easy to read L.E.D’s. Provides automatic independent testing for TDMS Red, TDMS Green, TDMS Blue, TDMS Clock, CEC, 12C Clock, 12C Data, 5Vdc, and Hot Plug. Can be used to test DVI cables by using the optional Calrad 35-716 DVI to HDMI adapter. Works with all formats of HDMI and DVI cables.