Electrical wiring, circuit, energization, and resistance test apparatus

Claim 1

Industrial wiring, circuit, energization, and resistance test apparatus having acoustic output to test for line resistance, insulation resistance, or voltage levels and polarities arising in an electrical sample network comprising a two-stage electrical oscillator-amplifier circuit (1, 2, 3, 4, 5) having two transistors (1, 2) connected in cascade, and an R/C circuit (3, 4, 5), the relative values of resistance and capacity of which affect the frequency of operation thereof, the capacitor (3) of said R/C circuit connecting the output of the second transistor (2) to the input of the first transistor (1) to provide for feedback of said oscillator circuit, said first transistor (1) having a bias circuit including a high value resistor (5) of said R/C circuit and forming a portion of the bias circuit; audio transducer means coupled to said oscillator circuit for reproducing the tone thereof; a source of d-c voltage (17) and a low resistance connection (17'') from said sources to the transistors (1, 2) of the oscillator circuit; test connection means (15, 16) to which the sample circuit is connectable; and switch means (S'') connected to said test connection means and to the oscillator circuit to selectively connect: a. when the switch means is in one position, the test connection means (15, 16) in parallel to the resiStor (5) to test the sample network for a-1. insulation resistance between test connection means to check for insulation of an open circuit between said test connection means, the value of the total resistance being introduced by the resistor (5) and the insulation resistance connected in parallel thereto determining and controlling the pitch of the tone reproduced by the transducer means as an analog of said total resistance, or a-2. voltage levels therein, in that introduction of a foreign voltage to the test connection means will affect the bias voltage across resistor (5) and disturb the balanced state of the oscillator circuit to change the frequency of oscillations to a different pitch whereby the level and/or polarity of the foreign voltage source can be determined; and b. when the switch means is in another position, the test connection means (15, 16) in series with said d-c source (17) and the low resistance connection (17'') to interrupt the circuit from said source to the oscillator means unless the sample network has ZERO, or essentially ZERO or low resistance to provide an output test oscillation from the oscillator circuit, the pitch of which is indicative of the resistance of the sampling network placed in series between said source and the oscillator circuit.