Containing network of precision resistors for checking resistance and 2 diodes for checking diode polarity, Model CB50 allows users to determine empirically whether CableEye® cable and harness tester requires calibration. Ten different resistance values are checked in triplicate at each of tester header’s 64 test points. CB50 attaches to tester like regular connector board. When checking expansion modules, board can be connected directly or via extension cable.