CableEye Models M3U and M4 look identical on the outside. Internally, M4, shown below, uses a different circuit board that enables it to measure capacitance. This photo shows catalog Item 824, the CableEye M4 system with the CB18A 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 M3U system, M4 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 M4, Item 825 (vertically stacked). USB interface standard. A computer is required even though one is not shown in this photo.