Improving fault diagnostic resolution of an oscillation-based test methodology scheme for the threshold detector circuit

This paper presents a simple design for test, an oscillation-based test methodology (OTM) scheme for a threshold detector circuit which is commonly used in telephone tone ringer applications. The method proposed is based on a three-phase testing procedure. In phase one, OTM is employed to achieve high fault coverage without the need for test generation. This is followed by the measurement of the power supply current in phase two to identify and locate faults. In phase three, node voltage measurements are utilized to further improve the fault diagnostic resolution.