Abstract: An insulation tester and oscillator circuit for use in same includes a transformer including a primary winding and at least one secondary winding to be coupled across an external load such as an electrode. First and second bipolar junction transistors are connected in a “push-pull” operating mode and coupled to the primary winding of the transformer for producing a high frequency voltage. The primary winding has two ends each respective one of which is coupled to a respective one of the collectors of the first and second bipolar junction transistors. First and second field effect transistors are respectively coupled in parallel with the first and second bipolar junction transistors. An actuator for activating the first and second field effect transistors to respectively conduct substantially synchronously with the first and second bipolar junction transistors shortly after start-up is provided, whereby the majority of current is shunted through the field effect transistors.

Abstract: An insulation tester and oscillator circuit for use in same includes a transformer including a primary winding and at least one secondary winding to be coupled across an external load such as an electrode. First and second bipolar junction transistors are connected in a “push-pull” operating mode and coupled to the primary winding of the transformer for producing a high frequency voltage. The primary winding has two ends each respective one of which is coupled to a respective one of the collectors of the first and second bipolar junction transistors. First and second field effect transistors are respectively coupled in parallel with the first and second bipolar junction transistors. An actuator for activating the first and second field effect transistors to respectively conduct substantially synchronously with the first and second bipolar junction transistors shortly after start-up is provided, whereby the majority of current is shunted through the field effect transistors.

Abstract: An insulation tester and oscillator circuit for use in same includes a transformer including a primary winding and at least one secondary winding to be coupled across an external load such as an electrode. First and second bipolar junction transistors are connected in a “push-pull” operating mode and coupled to the primary winding of the transformer for producing a high frequency voltage. The primary winding has two ends each respective one of which is coupled to a respective one of the collectors of the first and second bipolar junction transistors. First and second field effect transistors are respectively coupled in parallel with the first and second bipolar junction transistors. An actuator for activating the first and second field effect transistors to respectively conduct substantially synchronously with the first and second bipolar junction transistors shortly after start-up is provided, whereby the majority of current is shunted through the field effect transistors.

Abstract: An insulation tester and oscillator circuit for use in same includes a transformer including a primary winding and at least one secondary winding to be coupled across an external load such as an electrode. First and second bipolar junction transistors are connected in a “push-pull” operating mode and coupled to the primary winding of the transformer for producing a high frequency voltage. The primary winding has two ends each respective one of which is coupled to a respective one of the collectors of the first and second bipolar junction transistors. First and second field effect transistors are respectively coupled in parallel with the first and second bipolar junction transistors. An actuator for activating the first and second field effect transistors to respectively conduct substantially synchronously with the first and second bipolar junction transistors shortly after start-up is provided, whereby the majority of current is shunted through the field effect transistors.

Abstract: A variable inductance transformer includes a core defining a gap between opposing first and second ends. A primary winding and at least one secondary winding are coupled to the core. The secondary winding is provided for stepping up the voltage across the primary winding. A carriage assembly includes a magnetic shunt movable against the core and variably across the gap. The magnetic shunt has a width at least as wide as the gap for moving the shunt to a predetermined position along the core in a range from an uncovered position not overhanging the gap, throught intermediate positions overhanging the gap, to a covered position where the shunt bridges the gap. A control circuit controllably energized a motor to move the carrriage assembly and position the magnetic shunt against the core for adjustably varying the inductance of the secondary winding a to maintain a high output voltage of the transformer for a given resistive supply current.

Abstract: An apparatus for testing the insulation of an insulated electrical conductor has an alternating current high voltage power source which provides a high test voltage between the electrical conductor and an electrode to reveal defects in the insulation. A high Q antiresonant circuit, tuned to a predetermined frequency, is connected in series with the electrode and power source for shunting most frequency components of the corona and noise currents to ground and for non-shunting an insulation fault voltage of the predetermined frequency resulting from an arc current due to a defect in the insulation. The fault voltage signal non-shunted by the antiresonant circuit is provided through a coupling impedance to a transmission cable having a pair of twisted wires for transmission to a remote location. Impedance matching transformers, coupled to both pairs of ends of the twisted wires, are tuned to the same frequency as the antiresonant circuit to minimize attenuation of the signal.

Abstract: A method and related apparatus for sensing and indicating the location of a "hot spot" along a temperature sensing cable utilizes a linear stable voltage feedback loop circuit for maintaining a predetermined magnitude DC voltage across one conductor of a pair of conductors having electrically insulating jacket compositions which become electrically conductive when the temperature at any location along the surface exceeds a predetermined temperature wherein the voltage measurement is a direct indication of the distance from the NEAR END of the temperature sensing cable to the "hot spot".

Abstract: Apparatus for testing the insulation on an insulated conductor wherein a high AC test voltage is applied to an electrode through which the insulated conductor is passing is presented and includes a testing station for applying the high AC test voltage potential to an electrode at a desired magnitude and frequency. Current induced in the electrode due to corona effects or arc current pulses due to a defect in the insulation are sensed by a current sensing transformed circuit to develop a insulation condition voltage signal. The insulation condition voltage signal together with a low voltage test signal proportional to the magnitude of the high AC test voltage potential are coupled to a remotely located controlled unit. A negative peak detector receives the low voltage potential to produce a bias voltage at the input to the fault detection circuit.

Abstract: Apparatus for testing and counting flaws in the insulation of an electrical conductor includes an oscillator for generating an alternating test voltage which is used with an electrode to apply a hight test voltage to the insulation of a conductor passing through an electrode wherein the test voltage arcs to the current carrying conductor through an imperfection or flow in the insulation. A fault detection circuit uses a negative threshold voltage upon which the peaks of the alternating test voltage ride and includes a peak rectifying circuit which rectifies the positive excursions of a ringing signal inpressed on the peaks of the test voltage to produce a fault present voltage signal. The oscillator is part of a control loop which includes a full wave precision AC-to-DC converter which provides an output signal to an amplitude controller circuit which adjusts and maintains the magnitude of the alternating test voltage produced by the oscillator at a desired preset value.

Abstract: An insulated wire having one end grounded is passed in an unaltered path through an unconfined stream of water to which an electric potential has been applied. Faults, such as pinholes or voids, in the insulation are detected by a current flowing from a variable voltage power source through the wire to ground. A fault indicator provides a signal responsive to the current flow.Water is replenished by dripping individual droplets from a faucet into the testing apparatus to establish electrical isolation between the water faucet and the testing apparatus.

Abstract: A band marking apparatus for producing marking bands at spaced intervals along an insulated wire employs two ink jet dispensers located on opposite sides of the moving wire at longitudinally spaced stations. The dispensers are driven in an oscillatory manner by means of a tachometer engaged with the wire so that the marking bands are produced at uniform intervals regardless of the speed of movement of the wire past the dispensers. To insure proper registration of the band segments produced by the respective dispensers on opposite sides of the wire, an electronic controller for the dispensers includes an adjustable phase selector to regulate the phase relationship of the oscillating dispensers. The controller also includes other circuitry to maintain linear signal relationships and to center the oscillations of the respective dispensers on the wire.

Abstract: A continuous continuity monitor checks the continuity of an electrically insulated wire as the wire is moved axially of itself through the monitor, and provides an appropriate signal whenever a break in a conductor within the wire is detected. The monitor employs two detecting electrodes spaced along the wire and an excitation electrode to which a high frequency voltage is applied. The conductor within the wire is grounded at one side of the detecting electrodes opposite from the excitation electrode to complete a capacitive circuit with the excitation electrode. As the wire is moved past the electrodes, the same excitation voltage is capacitively coupled from the conductor to the two detecting electrodes as long as there is no break in continuity.

Abstract: A remotely controlled high potential dc insulation tester includes a dc power supply and a high voltage electrode mounted within a rotating mechanism and performs insulation tests on conductors which are within the same rotating mechanism. The power supply receives low voltage electrical power from outside of the rotating mechanism, and is monitored and controlled from a remote station in a non-rotating environment. Detecting circuits at the remote station determine the number of faults in a conductor drawn past the electrode and identify large faults such as bare-wire intervals along the conductor.

Abstract: A collapsible speaker assembly is formed by a split case in which a plurality of individual speakers are mounted. The split case is formed by two mating shells which are pivotally connected together at one side. When the shells are opened in 180.degree. relationship with each other, a sound column is formed in which the speakers are held in a generally linear array. In use, the sound column is held in a vertical position for improved dispersion of sound in the horizontal plane of an audience.