Electronic voltage and continuity testing unit

Claim 1

Testing apparatus having the capability of effecting a single voltage pole mode of testing and of effecting a continuity mode of testing, said apparatus comprising: (a) first and second testing terminals; (b) a loudspeaker; (c) a battery energized oscillator circuit coupled to energize said loudspeaker and having a control input, said second testing terminal being coupled to said oscillator circuit; (d) a control transistor having a base, an emitter and a collector; (e) first and second resistances, said first resistance being connected in circuit between said base and said emitter of said control transistor, the battery being connected through said emitter and collector of said control transistor to said control input of said oscillator circuit, said first testing terminal being connected through said second resistor to apply an AC voltage component to said base of said control transistor; (f) said first and second resistances being valued such that when a test alternating voltage component is applied solely to said first testing terminal, a sufficient voltage appears upon said first resistance for the control of said control transistor; (g) said oscillator circuit operative in a continuity mode upon the ohmic connection of said first and second testing terminals, whereby a voltage is applied to said base rendering said control transistor conductive and applying an enable signal to said control input to render said oscillator circuit into an oscillating state thereby producing an oscillator output signal energizing said loudspeaker, and operative in a single pole voltage mode, whereby an alternating voltage component as applied solely to said first testing terminal is imposed across said first and second resistances to render conductive said control transistor and to apply an enable signal through said conductive control transistor to said control input to render said oscillator circuit to its oscillating state, thereby producing an oscillator output signal modulated by the frequency of said alternating voltage component energizing said loudspeaker.