CableEye Models M2U and M3U look identical on the outside. Internally, M3U, shown below, uses a different circuit board that enables it to measure resistance. This photo shows catalog Item 821U, the CableEye M3U system with the CB15 board set attached. Remove the interchangeable CB boards by pressing apart the latches near the front of the board. Choose from over 60 different CB boards to accommodate over 200 standard connector types, and use the CB8 board for prototyping and circular connectors accomodating unlimited connector types. Like the M2U system, M3U offers a small bench footprint and the ability to handle cables of up to 76 conductors. For larger cables or harnesses, attach an expansion module to M3U, Item 823 (vertically stacked). See below for rear view and side view. USB interface standard. A computer is required even though one is not shown in this photo.