Compensation method and apparatus for use with nonideal test access lines

摘要

An arrangement to compensate for the leakage and biasing characteristics associated with the semiconductor crosspoints of a concentrator to allow accurate telephone subscriber loop measurements to be made through the concentrator. A compensation current is supplied which varies linearly with the applied test voltage according to a relationship that is determined adaptively just prior to the test so that the effects of device differences and temperature variations are minimized. The approach is extended to nonlinear compensation.