Electrical circuit voltage and continuity testing device

Claim 1

In a circuit testing device, the combination comprising (a) a casing, (b) a single probe rigidly projecting from said casing whereby the casing may be manipulated to forcibly insert the probe into an electrical power socket, there being a Zener diode connected in series with the probe, (c) a presence-of-voltage circuit in the casing and electrically connected with the probe, said circuit including a presence-of-voltage indicator, and rectifier means and amplifier means electrically connected between the probe and the indicator, the rectifier means including a rectifier bridge having two terminals connected across the Zener diode, there being a half-wave-rectifier connected in series between the Zener diode and the probe, (d) said amplifier means including first and second Darlington amplifier stages electrically connected between the rectifier means and the indicator, said first and second stages comprising first and second transistors each having base, collector and emitter electrodes, the first transistor base electrode electrically connected with a third terminal of the rectifier means, the second transistor base electrode electrically connected with one of the emitter and collector electrodes of the first transistor, there being a battery connected in series with the indicator, the battery and indicator connected between the collector and emitter electrodes of the second transistor, (e) there being a voltage level testing circuit electrically connected with the probe, (f) and there being an electrical continuity testing circuit operatively connected with the probe, via said Zener diode.