Novel techniques for locating open faults in a complex switch matrix

A complex switch matrix is composed of many crosspoint switches which are operated independently to complete a path through the matrix. If one of these crosspoints fails to close, it would be necessary to involve additional crosspoints in a loopback test arrangement or do a manual continuity check to locate the defective crosspoint. Using the techniques described here, only one access point is required to the crosspoint under test, and no manual probing is required. These techniques make use of simple oscillator circuits to effect measurements of frequency or phase shift when the state of the matrix is changed. Reliable results are obtained with this method, which can be performed quickly and automatically under the control of an auxiliary single-chip microcontroller