versatile logic probe

A logic probe is a useful aid to testing and fault-finding digital circuits. The many commercial and amateur designs currently available all provide information about static logic states and a few also provide information about the dynamic behaviour of the circuit. The versatile logic probe provides information about logic levels and the duty-cycle of pulse trains in TTL and DTL circuits and is unusual in that it uses a 7-segment LED display for the readout, instead of the more usual discrete LED`s.