Abstract: A double-sideband amplitude modulated (DSBAM) carrier passed through band-pass circuits wich are too narrow for the modulated carrier or are misaligned, may have one or both side-bands altered in relative amplitude, or in phase relative to the carrier. These effects result in amplitude modulation distortion and produce angle modulation of the carrier, with the same waveform as the amplitude distortion. In this invention the angle modulation is detected and applied to an amplitude modulator in the required phase and amplitude to substantially eliminate the distortion of the modulated carrier.

Abstract: Receiving apparatus for a message occupying a message frequency band which simultaneously may include noise, and includes one or more unmodulated or amplitude-modulated double-sideband constant-frequency carriers with or without carrier suppression as periodic signals, which uses sampling and reconstruction circuits to deliver the message substantially free from the periodic signals, and to deliver each periodic signal substantially free from noise, the message and any other periodic signal present in the message frequency band.

Abstract: A syllabic compandor using a pilot in the signal frequency band, with a compression ratio between approximately 2 and 20, including a frequency and delay equalizer in the negative-feedback loss-control circuits of the compressor and expandor, to permit high compression and expansion ratios without positive feedback at any frequency or signal level, the expansion ratio materially less than the compression ratio in some cases, and sampling at more than the Nyquist frequency for the signal band to remove any unwanted periodic wave such as the pilot wave, lying in the signal frequency band, from the output, without altering phase and amplitude of other waves in the signal frequency band.

Abstract: In receiving apparatus for a double-sideband amplitude-modulated wave, a synchronous detector which samples the modulated wave for short periods centered on instants of peaks of the carrier at regularly-occurring intervals, with a sampling frequency greater than the Nyquist frequency for the modulating wave, equal to the carrier frequency divided by an integer, and reconstructs the modulating wave from the sequence of samples in a reconstruction filter. This detector has a high output signal-to-noise ratio and produces a distortionless output with positive or negative overmodulation, and with reduced or suppressed carrier.

Abstract: This invention provides improvements of noise-reducing apparatus for a signal with superimposed noise. The improvement comprises means for double sampling of a signal with the instants of zero-crossings known or ascertainable at the receiving apparatus and with superimposed noise each sampling carried out at intervals not greater than the Nyquist interval for the signal, to produce two interlaced sequences of samples, reconstructing the signal plus superimposed noise from the first sequence of samples, taken at instants near peaks of the signal, reconstructing the superimposed noise only from the second sequence of samples, taken at instants of zero-crossings of the signal, and subtracting the reconstructed superimposed noise from the reconstructed signal plus superimposed noise, to produce the signal substantially free from the superimposed noise.

Abstract: Receiving apparatus, for a signal consisting of a carrier amplitude modulated by a first program and angle modulated by a second program, which delivers the programs separately and indicates a dual-modulation signal is being received, for use in a-m stereo and a-m dual-program systems.

Abstract: An amplifier for a band-limited signal, which produces an amplified output signal by sampling the input signal at a frequency greater than the Nyquist frequency for the signal frequency band, quantizing the signal samples, activating one or more of a plurality of output leads for each quantized sample, actuating switches by the activated quantizer output leads to charge and discharge one or more capacitors in the interval between adjacent samples through windings of an output transformer, and filtering the output of the transformer to produce an amplified quantized replica of the input signal. High power and high efficiency are obtained with moderate voltages and capacitor values, and with available switching devices, for signals with a Nyquist frequency up to several hundred kilohertz.

Abstract: Steady-state evoked potentials from the nervous system, measured on the scalp and elsewhere on the body in response to specific periodic sensory stimuli, contain the fundamental frequency of the stimulus and other waves, and are of the order of 40 dB below potentials due to general electrical activity of the nervous system which may be considered as noise. Medical information revealed by evoked potentials is extremely valuable but is limited by measuring methods of the prior art and by the background noise. In this disclosure the periodic steady-state evoked potential from a periodic stimulus, shifted to a suitable frequency band, is sampled at instants of zero-crossings of the shifted evoked potential, at the Nyquist frequency or greater for the noise frequency band, and the resultant samples of noise are reconstructed in a filter and subtracted from the entire evoked potential, to produce as a resultant the evoked potential substantially free from background noise.

Abstract: An angle-modulated transmitter generates a two-channel stereo wave by double-sideband angle modulation of a carrier with a first signal, double-sideband angle modulation of the same carrier, delayed less than 90.degree., with a second signal, and addition of the two modulated waves linearly, or an equivalent method, to produce a combined wave from which the two signals can be readily separated, which can compatibly be received by an f-m mono receiver, and which occupies the frequency band of a mono channel of the same bandwidth and deviation ratio.

Abstract: An aircraft carries a pressure indicator well in advance, which may record barometric pressure of vertical air currents. The indicator reading is converted to electric current and averaged over a short period. The unaveraged current at a given position of the pressure indicator is recorded, delayed, read out, compared with the average current and the error current used to actuate wing flaps at the instant the wings pass over the given position, so as to adjust the wing lift for any difference in conditions as the wings move forward. Similarly the current recorded at the instant the pressure indicator was at a given point is delayed, compared with the average current at the instant the tail structure passes over the given point, and the error current is used to adjust elevators for any difference in pressure as the tail structure moves from its first position to the position of the pressure indicator at the given instant.

Abstract: Steel wire rope used for lifting and hauling is dangerous when stressed above the breaking point, as there is a substantial quantity of energy stored in the stretched rope and when the rope breaks the stored energy causes the broken ends to whip at high velocity, in a number of recorded cases causing fatalities, and serious damage to helicopters, cranes, vessels and vehicles. This invention discloses a steel wire rope with a strong hand elastic sleeve or sleeves which are not in longitudinal tension, and which dissipate by friction the energy stored in the broken cable, thus materially reducing the possibility of damage to the surroundings.

Abstract: A system for modulation of the amplitude of a d-c voltage, the amplitude of an a-c carrier, or the frequency of an a-c carrier by signal, in which the signal amplitude is continuously compared against a predetermined series of equally-spaced d-c voltages, and coincidence-sensing and switching means associated with each d-c voltage connects a corresponding d-c voltage to the output circuit in the case of an instantaneous compressor, an instantaneous expandor or a signal amplifier, connects a carrier of corresponding amplitude to the output circuit in the case of an amplitude modulator, and connects a carrier of corresponding frequency to the output circuit in the case of an angle modulator.

Abstract: A lens comprising a plurality of identical straight optical fibers arranged in a bundle with at least a portion of each fiber treated to suppress internal reflections, so that each fiber transmits only rays which enter the end of the fiber substantially parallel to its axis at that point, the angle between adjacent fibers of the bundle of optical fibers being adjustable to provide a lens for a range of solid angles, with a field of any shape and an image adjustable in size which may be altered in location and plane, by extending the optical fibers by flexible sections with internal reflections permitting transmission of rays on curved paths.

Abstract: Means and method for generation and combination at a transmitting apparatus and separation and demodulation at a receiving apparatus of two signals comprising carrier waves of the same frequency but having different phase, modulated with different programs. Receiving apparatus according to this invention eliminates one of the signals in each of its two channels by sampling the combined wave at instants of zero crossings of the carrier of that signal, at a rate at least twice the highest program frequency, and then integrating the sequence of samples so produced to give the program of the other signal. Thus this system provides relatively simply compatible a-m stereo transmission, or a-m transmission of two unrelated programs on a single carrier.

Abstract: The method of transmission of a carrier double-sideband amplitude-modulated by a message, comprising sampling the modulated wave at regular intervals at a sampling rate greater than twice but less than four times the highest message frequency, with the sampling rate an integral sub-multiple of twice the carrier frequency of the modulated wave, the instants of sampling not occurring at instants of zero crossings of the carrier, and subsequent reconstruction of the modulated wave or the message from the sequence of samples in an integrating filter, with substantially complete accuracy.

Abstract: This invention discloses an automatic focusing device for cameras and other optical apparatus which comprises scanning means for at least a portion of the focused image, and the scanning current varies the focusing means automatically until the scanning current shows a maximum of high-frequency component to low-frequency component power.

Abstract: A transducer for generating pressure waves from electrical signal waves, in air, water or other fluid, which consists of a plurality of orifices in a vessel containing the transmission fluid under pressure, each orifice being controlled by a valve, which in turn is controlled by one of a plurality of output leads from a quantizing circuit, which is activated by samples of the signal wave taken at the Nyquist rate or faster. A quantized sample of a given amplitude causes a valve or valves covering orifice or orifices to open, to permit an emission of fluid, proportional in energy to the energy contained in the quantized signal sample.

Abstract: This invention provides a method and means for amplifying signal waves with high efficiency that comprises signal sampling means operating at the Nyquist rate or greater, sample-quantizing means, a plurality of circuits that link the quantizing means to a plurality of controlled current-switching means, combining means that combines the outputs of the plurality of switching means, and filter means that reconstructs an amplified facsimile of the signal.

Abstract: The electric induction heating in situ of a selected portion of an underground coal deposit, for the purpose of facilitating extraction of gases, liquids, solids and energy from the deposit. The heating is conveniently effected by passing a time-varying electrical current through a conductor encompassing the selected portion. The conductive path is preferably a toroid, quasi-toroid, helix, or simulated toroid, quasi-toroid or helix, created by a drilling and passing one or more conductors through the drill holes.

Abstract: An inductor comprises a quasi-toroidal conductive envelope having a discontinuity across which alternating voltage may be applied. The inductor may comprise a plurality of interrupted turns connected in parallel or may be formed by a continuous conductive shell. The cross-section of the envelope may be circular, rectangular, or shaped in any other desired manner. Capacitive elements may be arranged within the interior of the device to form a resonator.