Abstract: The phase range of a phase detector is extended while maintaining its modulation bandwidth and linearity. The range is widened by dividing down the frequencies to be compared. Clocked delay lines create sequentially delayed multiple-phase signals which are applied to a plurality of component phase detectors. The outputs of each of the component phase detectors are summed to restore the frequency of the original clock signals to the output components. This technique is especially useful in high-speed phase detectors.

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: Systems for synchronizing a pseudorandom binary sequence signal with a time-delayed version of the same signal without the use of delay lines or programmable counters. This is accomplished by the use of two Pseudorandom Binary Sequence [PRBS] generators for producing the same PRBS signal. Each PRBS generator incorporates as a constituent component a serial shift register with M stages with the outputs of multiple stages fed back through an exclusive-OR to provide an input to the register, thereby to produce a clocked repetitive series of said sequence signal as inputs to each register. The states of shift register are numbered n such that (n-1) clock cycles elapse before the next start state. A start detect circuit is responsive to the start state of the pseudorandom binary sequence signal of the first generator for generating a synchronizing signal at that instant to force the second PRBS generator to be at a state in the binary sequence representing a delayed point in the sequence.

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: This invention provides mechanisms that detect the large dynamic range of radiant intensities in the natural environment, that use novel strategies to calculate an approximation of visual properties of objects, and that represent a scene with an image having a specific dynamic range that is optimal for display media such as photography, television and printing.Photographs and other images are made according to the foregoing mechanisms from lightness fields produced from multiple comparisons between information associated with a different segmental areas of an image field. Different comparisons involve different groups of segmental areas, and different groupings have at least one spatial parameter different from other groupings of areas. Comparisons advantageously are made in succession with an ordered sequence of the spatial parameter and employing results of prior comparisons.

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: 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.