Abstract: An apparatus and method for detecting telephony signaling states, comprises an analog to digital converter and a microcomputer with associated firmware for controlling the operation of the microcomputer. The analog to digital converter digitizes incoming analog voltages containing telephony signaling state information and presents the digitized data samples for operation by the microcomputer. The microcomputer performs various digital filtering and analysis of the digital data samples in order to determine the signaling states represented by such digital data samples, and upon detection of the signaling states, outputs information indicative of such detected states. The present invention also incorporates use of such a detection circuit within line cards used to interface telephone subscriber lines with the central office terminal. The present invention further encompasses the methodology of performing such digital data sampling and analysis so as to determine telephony signaling states.