Computer-aided probe with tri-state circuitry test capability

Claim 1

A computer-aided network comprising: a dual threshold detector having a signal input, a high reference input, and a low reference input; probe means having a tip for contacting circuit check points; means connecting the detector signal input to the probe; first programmable means for generating analog high and low reference signals for the high and low reference inputs of the detector; and memory means connected to the output of the detector for storing an output signal from the detector signifying the detection of a probe signal level between the low and high reference values; a circuit for checking tri-state operation of a circuit check point, the circuit comprising: first and second resistive means respectively connected to the high and low reference signals; switch means connecting the resistive means in parallel to a probe tip for producing a programmable voltage at the tip; wherein the tip voltage remains substantially constant when the tip contacts a circuit check point operating in a tri-state condition; the network further including trigger means connected to the detector output for generating a toggling signal in response to sequentially alternating pulses at the detector output signifying that a circuit check point is producing a normal binary signal.