Abstract: Diverse methods for eliminating potentially harmful periodically varying electrical and magnetic fields which emanate from electric blankets, heating pads, and other electrical appliances intended for use proximate to the human body. One approach entails the use of a self-shielding coaxial cable as the heating element with core and sheath connected electrically in flux-cancelling fashion to minimize emanated magnetic and electrical fields. Another approach involves the use of heating elements, may otherwise be of currently conventional construction, powered with filtered dc to avoid potentially harmful alternating fields and produce harmless stationary fields instead. Ground integrity assurance means are also provided to avoid the emanation from the blanket or appliance of alternating electric fields which might otherwise result from connection to an improperly polarized alternating current source.

Abstract: Several phenomena which occur commonly in graphite composites, as well as other materials, and which affect the impedance of an eddy-current probe have been characterized on the complex impedance plane. An eddy-current method is disclosed by which a target material is stimulated at several frequencies, the impedance of the probe is measured and compared to the impedance of reference material, and the condition of the target material is determined. The method described is capable of finding the signatures of a number of conditions commonly found by eddy-currents, and can be programmed to find others, such as conductive and non-conductive plating thicknesses, and inclusions of material with relative ferrous materials. Because the method determines faults on the normalized impedance plane, it is capable of being used on other conductive materials in addition to graphite composites.

Abstract: In connection with a beverage dispensing machine, an automatic self-fill control apparatus for the machine for controlling the filling of the liquid tank, which liquid tank is fed with a combination of water and a concentrate syrup adapted to be mixed with the water within the tank. A sensor member is disposed in the tank in a position so as to be responsive to the rise and fall of liquid in the tank. Pump means are provided adapted to pump the syrup to the tank. Control of water flow to the tank is also carried out. The sensor member has a low probe for detecting a low predetermined level of liquid in the tank and a high probe for detecting a high predetermined level of liquid in the tank and adapted to respectively generate low and high probe signals.

Abstract: A coil assembly that is essentially isotropic in a plane normal to the plane of the coil includes two flat coils stacked one next to the other. One coil is connected in series with a resistor in a closed loop and has a strip of high permeability material woven through it. The other coil is tuned by a parallel capacitor across its coil terminals, such terminals being connected to electronic circuitry. The coil is separated from the printed circuit board that contains the electronic circuitry by a sheet of high permeability material. The assembly is self-contained and powered by a flat battery on which the circuit board is placed. Another embodiment is disclosed that contains only one coil, the terminals of which are connected to a suitable electronic circuit, not shown. Strips of high permeability material are disposed on both sides of the coil and an assembly is produced with a printed circuit board and a flat battery.

Abstract: A coil assembly that is essentially isotropic in a plane normal to the plane of the coil includes two flat coils stacked one next to the other. One coil is connected in series with a resistor in a closed loop and has a strip of high permeability material woven through it. The other coil is tuned by a parallel capacitor across its coil terminals, such terminals being connected to electronic circuity. The coil is separated from the printed circuit board that contains the electronic circuitry by a sheet of high permeability material. The assembly is self-contained and powered by a flat battery on which the circuit board is placed. Another embodiment is disclosed that contains only one coil, the terminals of which are connected to a suitable electronic circuit, not shown. Strips of high permeability material are disposed on both sides of the coil and an assembly is produced with a printed circuit board and a flat battery.

Abstract: A duplexer is provided in which a transmit input signal is fed in parallel through two autotransformers to a pair of portal loops for establishing an interrogation field. Significantly lower voltage response signals returning via the autotransformers are applied in push-push relationship to the primary of one transformer for producing a difference signal output, and in parallel to a second transformer primary for producing a sum signal output. Back-to-back diodes across the secondary windings of the sum and difference output transformers limit the volt drop across the respective primaries for the relatively higher voltage transmit input signal. The response signal, however, is below the threshold of the diodes and, consequently, the diodes do not attenuate such signal.

Abstract: The timer controls a dispensing machine and in particular controls the dispensing cycle for a product such as coffee, a beverage, or instant mashed potatoes. The control includes regulation of the water portion of the cycle and the solid or powder portion of the cycle. The timer is controlled by a plurality of touch switches each coupling via a resistor network to the control logic of the timer. The control logic is preferably CMOS-type having a high input impedance permitting use of a resistor network of high resistance to limit current flow especially under fault. The touch switches control functions such as "hot water", "large portion", "small portion", "stop", and "push and hold".

Abstract: A bidirectional semiconductor switch such as a Triac in the usual failure mode, wherein the device conducts continuously in only one direction, has a storage circuit in series intermediate the triac and load. The storage circuit may comprise a single capacitor preferably of predetermined value and adapted to, after a relatively short time-out period, interrupt power applied to the load. The capacitor is preferably a non-polar type, although, in an alternate embodiment a pair of oppositely-poled polar capacitors may be employed.

Abstract: The drive circuit operates a shaded pole motor having in the disclosed embodiment three windings of turns N, N/2 and N/2. The control is basically two-speed control with the lower speed operation being adjustable by means of the drive circuit and with the high speed operation being directly from the AC line. The drive circuit includes a clock, frequency adjustment means, power inverters and unilateral means for limiting power consumption.

Abstract: An electrodeless conductivity measuring system of the type employing a spaced pair of toroidal ferromagnetic cores, in which anomalies in the permeance of the cores is alleviated by the use of non-permeable shields of conductive material.

Abstract: Ground fault protective systems are disclosed in which fault signals are generated in response to differential currents carried by electrical supply lines. A circuit breaker interrupts power on the supply lines when the fault signals exceed a given magnitude and duration. Downstream reactances to ground from one or more supply lines give rise to spurious fault signals which do not characterize true ground fault conditions. These spurious fault signals are cancelled prior to detection by means of neutralizing auxiliary circuits. The resulting fault signals exhibit a high signal-to-noise ratio.

Abstract: A braking system for three phase motors without an accessible neutral terminal comprising a current limiting motion detection circuit that is energized when the motor is energized or is being supplied with braking current as long as the rotor is in motion, a DC braking circuit, and a control circuit actuated by a stop command that disconnects the source from the motor and supplies braking current until the rotor comes to a stop. A ferroresonant motion detection circuit is disclosed that is also useful in braking systems for other motor types.

Abstract: A transformer circuit is arranged to attenuate spurious signals at undesired frequencies and substantially reduce the distortion of signals coupled through the transformer. The transformer circuit includes an iron core transformer and an active circuit arranged to simulate a lumped element having a frequency dependent magnitude which resonates with the transformer impedance at a desired frequency.

Abstract: Apparatus including polarity sensing means and a switch such as a Triac for providing a ground fault circuit interrupter system for an electrical load such as a hand-held appliance. The Triac is electrically connected in a completed circuit with the electrical load and is positively positioned in series with the line conductor of an A.C. power source. Automatic testing circuitry such as introducing synthetic and counterbalancing synthetic faults to the system is included.

Abstract: To minimize nuisance tripping for spurious causes in ground fault protective systems, fault-characterizing signals derived from differential currents in alternating current supply lines are subjected to a variable integration automatically adapted to the magnitude of the fault-characterizing signal. Higher level signals are integrated at augmented rates, preferably with an antilog characteristic. The supply circuit is interrupted when the expanded and integrated signal exceeds a threshold value.

Abstract: A sound motion picture system in which sound is recorded on movie film. A constant speed capstan drives the film past a sound transducer, and a claw drives the film incrementally past a film gate. A projection lamp, a DC power supply, and an induction motor for driving the claw are energized from a common source. A film loop between the transducer and the film gate controls a switching circuit for unbalancing the current to the induction motor to control the speed of the motor without materially affecting the rms value of the current supplied to the lamp or the peak - to - peak value of the voltage supplied to the DC power supply.