Abstract: Monitoring a leakage current from an isolator for a high voltage conductor to ground includes directing the leakage current through a primary wire inductively coupled to a secondary winding energizing an amplifier.

Abstract: A group of bushings receives voltage in parallel to produce a current output from each bushing. Cumulatively combining the current outputs from the bushings vectorially furnishes a vector sum bushing current. Reference voltage devices also produce reference current outputs. Cumulatively combining the reference current outputs vectorially provides a vector sum reference current, and differentially vectorially combining the vector sum reference current with the vector sum bushing current delayed by 90° provides a difference signal representative of a bushing condition. As an alternative to the reference voltage devices, a second group of bushings may be used. In this case, a delay of 90° is not required. The invention may also be used to monitor the condition of other capacitive devices, for example, high voltage current transformers.

Abstract: The invention features an apparatus and technique for amplifying a signal without creating a phase error. The apparatus is an active device with a restricted band width selected to include desired frequencies of operation. The apparatus includes at least one amplifier with a local feedback loop, formed by a network, constructed and arranged to exhibit a high forward gain at the operating frequencies. The amplifier and the network are constructed and arranged to provide substantially 180 degree phase shift between an input voltage and an output voltage at the operating frequencies. The apparatus also includes a signal input node adapted to introduce the input voltage to the inverting input of the amplifier, a signal output node adapted to obtain the output voltage from the output of the amplifier, and a resistive global feedback loop that connects the signal input and signal output nodes and controls the closed loop gain of the amplifying apparatus.

Abstract: The invention features power amplifying apparatus with controllable frequency characteristic of the gain. The apparatus includes a band pass network of two cascaded amplifiers and multiple resistors and capacitors arranged to form multiple feedback loops. The feedback loops stabilize the output A.C. signals and establish a predetermined bandwidth of the network. The apparatus also includes a capacitor resistor feedback loop, connected to the output of the second amplifier and input of the first amplifier, with the capacitor and the resistor selected to maximize the loop gain at a desired frequency.

Abstract: A current shunt device has main and auxiliary windings which are located in substantially the same position and are connected in series.

Abstract: A power controller includes a full-wave bridge rectifier circuit coupled to an A.C. line by a storage inductor with two windings and a saturating inductor. The output of the bridge rectifier is connected to a D.C. output terminal for producing output voltages for a symmetrical amplifier. The D.C. potential provided by the full-wave rectifier is compared with a ramp signal having an external ramp set point related to the D.C. output potential relative to a reference potential to provide a trigger pulse for controlling the time the SCR is gated on. A balancing system selectively switches auxiliary resistances in and out to maintain a desired balance. Upon sensing a gross imbalance, the SCR is turned off. The power controlling apparatus includes isolation circuitry for creating an isolation barrier having a high frequency path and a low frequency path. The high frequency path includes a transformer having main primary and secondary windings.

Abstract: A self-oscillating, high voltage DC power supply for a cathode ray tube drive. Included within the high voltage power supply are an oscillator coil connected to a DC supply and transistor switching means connected to the coil between the coil and ground so as to provide a charging circuit for the oscillator coil. Diode means and output filter are connected between the coil and the DC output to provide a smoothing of the ripple of the DC output. Included in the oscillator power supply are a feedback coil inductively coupled to the oscillator coil and wound in the opposite direction. The feedback coil is a part of a base drive circuit for the transistor switch. Included also are feedback resistance in series with the coil and these elements are connected between the base of the switching transistor and ground.

Abstract: The preamplifier comprises amplifying means, the output of which is inverted relative to the input, and a feedback circuit connected from the output to the input of the amplifier so as to provide a perfect integrator which cancels the amplitude variations resulting from changes in tape speed. The impedance of the feedback circuit and the impedance of the signal source extended to the amplifier are such that the output of the amplifier is the integral of the voltage generated in the inductive head over a wide band of frequencies.

Abstract: Improved slew recovery in a composite driving amplifier for driving a substantially reactive load including a feedback loop to the operational amplifier from the load for regulating the output of the amplifier, the composite amplifier has a predetermined resistance R1 in the feedback loop and includes a second feedback loop having a predetermined resistance R2. The second feedback loop extends from the output of the operational amplifier to the negative input and is substantially parallel with the first-mentioned feedback loop. To maximize the recovery of the amplifier from a slew condition, the relationship of R1-R2 should be as follows: ##EQU1## wherein: V.sub.o is the output voltage in the amplifier.Slope, is the slope of the load voltage curve during the overload condition, andDelay represents the period of time it takes the overload operational amplifier to respond to a feedback signal at a given overload condition.

Abstract: A system for the enhanced display of event markers in time-related association with physiological waveforms displayed on cathode ray tubes which use a recirculating memory to provide a refreshed display. The event is marked in the displayed waveform by an intensification of the normal trace determined by the time-related occurrence of the event and comprises a first modulation of the displayed waveform. A secondary event-controlled modulation of the primary modulated display serves to further enhance and accurately identify the occurrence and timing of the event marker in the display. This enhanced display of event markers is further utilized to distinguish a marker of one type from a marker of another type utilizing particular data coding in the memory and appropriate detection logic for recovering data from memory. The enhanced display is particularly useful for clearly marking events occurring in timed-relationship with a patient's cardiac cycle.

Abstract: An isolation amplifier comprising three separate conductively-isolated sections: (1) an input section including an AC modulator, (2) an output section including a demodulator, and (3) an improved oscillator or AC power section for reducing the undesirable effects of common mode interference signal sources coupled thereto through stray capacitance. The improved oscillator or power portion includes control elements for controlling the timing and direction of current conduction through the primary winding of a transformer having its secondary connected to the chopper or modulator. The control elements and circuitry associated therewith conduct in alternation and in a manner resulting substantially in conduction-overlap. Such conduction overlap is accomplished by means which accelerate initiation of conduction in one control element and possibly also retard the cessation of conduction in the other control element.