Osborne #13936T324 high impedance transformer has a 480 Volt, 60 Hertz primary and a no-load output of 120 Volts. Should the insulation of the motorette under test fail in a shorted condition, the impedance of this transformer has been calibrated to limit the shorted output current to 10 Amps RMS. The 120 Volt output is used to test the dielectric strength between turns of a winding. In addition to the impedance of this transformer, the circuit incorporates a circuit breaker in series with the output to trip and open the output circuit in a time no greater than three (3) seconds.