Abstract: A class D amplifier, suitable for use as a vertical deflection amplifier in a television receiver, includes two transistors coupled to function in a push-pull manner. Two diodes are serially coupled with each other in parallel with the output transistors and are poled to conduct forward current in a direction opposite to the forward current of the two transistors. A junction of the two transistors is coupled to a junction of the two diodes and forms an output terminal to which a deflection winding is coupled. A series of pulses at a first frequency, such as the horizontal deflection frequency or a multiple thereof, are pulse width modulated in accordance with the amplitude of a sawtooth waveform at a second frequency, such as the vertical deflection frequency, in a pulse width modulation stage and are coupled to the input terminals of the two transistors. The two transistors are alternately enabled for conduction by the pulse width modulated signals.

Abstract: In an instrument landing system for aircraft, the transmitter is required to produce an amplitude modulated signal comprising a carrier wave having sidebands containing the sum of a 90 Hz and a 150 Hz signal as modulation, and to also produce a double sideband, suppressed carrier signal in which the modulation is the difference between the 90 Hz and 150 Hz signals. In the present invention, the 90 Hz and 150 Hz signals are summed to provide a composite modulating signal that is employed to directly modulate the radio frequency carrier. To provide the double sideband signal the carrier is fed to a 180.degree. phase shift network, and the carrier and the network output are alternately delivered to a modulated amplifier stage by an RF switch which is operated with each change in the sign of a difference signal derived from the 90 Hz and 150 Hz signals. Accordingly, the output from the RF switch is a phasechanging carrier that undergoes a phase reversal with each change in the polarity of the difference signal.

Abstract: Display system capable of rapidly presenting three dimensional information ith a minimum of signal-to-noise degradation and particularly suitable for use in a high performance radar system. Three two-parameter display units present information on cathode ray tubes which include deflection circuits driven by main and auxiliary staircase sweep generators.

Abstract: An improved technique for eliminating interference in a signal processing stem exposed to multiple interference sources. A main receiving channel output and a plurality of auxiliary channel outputs are connected to form a canceller system where outputs from the canceller of each auxiliary channel are connected in parallel and subtracted from the main channel signal. The output residue from the subtractor is then combined in a second subtractor with the input from a second group of parallel connected cancellers using the same auxiliary channels. Each group of parallel connected cancellers and subtractor forms an iteration which reduces the residue of interference in the main channel. By providing a series of iterations, the cancellation obtainable can be improved along with an increase in system stability.

Abstract: A generator for controlling a transducer by means of sinusoidal wave trains is constituted by the association in series of a generator for producing wave trains formed by a whole number of half-cycles of periodic signals and of a filter which is tuned to the frequency of the periodic signals.

Abstract: A horizontal deflection system is operable either from rectified and filtered alternating current line voltage or from a substantially lower voltage direct current voltage source. The need for a step-down transformer in the receiver power supply is eliminated by utilizing the horizontal output transformer to drop the rectified and filtered alternating current voltage when the receiver is operated in the alternating current line mode. The horizontal output transformer is utilized as a step-up inverter when the receiver is operated from the low voltage direct current source to produce a direct current voltage at a point on the horizontal output transformer substantially equal to the rectified and filtered alternating current line voltage.

Abstract: A deflection circuit has a sawtooth generator with a control input and an output stage, each having a different power supply. A control voltage derived from the output stage supply is applied to the control input to decrease the flyback period as the output stage supply voltage increases.

Abstract: A Doppler navigation system with tracking filter for reducing suceptibility to multipath signals. For acquisition of a Doppler ILS angle representing a signal within a spectrum also containing multipath signals, a self-tracking variable-Q filter arrangement is used, with wide band acquisition (low Q) followed by progressive steering of the filter center frequency to the desired signal frequency, together with decrease of the filter bandwidth to an equivalent of 2 beamwidths (high Q) at final balance.

Abstract: A start-up circuit for a deflection system comprises a deflection circuit including a first oscillator which produces a first signal for producing a deflection signal in a deflection winding in response to the first signal. A second oscillator coupled to the first oscillator controls the frequency and phase of the first oscillator when a direct current potential is coupled to said second oscillator. A rectifying circuit coupled to the deflection circuit and the second oscillator provides the direct current potential to the second oscillator when the deflection signal is being produced.

Abstract: A field deflection output circuit in which the deflector coil is divided in two halves which are connected between the terminals of a direct-voltage source, in series during the trace interval and in parallel in the retrace interval. As a result the retrace interval may be given the correct duration whilst dissipation is kept low so as to enable the circuit arrangement to be integrated in a semiconductor body.

Abstract: Reliable cycle selection is achieved with LORAN-C pulses received under low signal-to-noise conditions. A tracking pulse is generated at the LORAN-C pulse repetition rate and is intended to be time-coincident with the end of the third 100 KHz carrier cycle in each received pulse. Sampling pulses are generated one-quarter and three quarters of a cycle before and after the tracking pulse and are used to sample a hard-limited, envelope-derived version of the received signal in which a phase reversal occurs at the start of the fourth carrier cycle. If the tracking pulse is coincident with the end of the third carrier cycle, a unique pattern of binary levels is sampled by the four sampling pulses. If the tracking pulse is too early or too late, corresponding early (left) and later (right) sampled level patterns result. Left and right occurrences of the tracking pulse are individually counted for a predetermined number of received LORAN-C pulses after which the difference between left and right counts is examined.

Abstract: The effectivenss of a seal for extinguishing fires in an underground mine passage is determined by transmitting acoustic energy from a first site toward the seal. The acoustic energy is detected at a second site on the opposite side of the seal from the transmitting site. To provide for remote monitoring of the seal, acoustic transmitter and receiver means are lowered into the passage to the first and second sites through vertical bores. The effectiveness of the seal is determined by the amplitude of the detected acoustic energy. The size of any hole in the seal is determined by comparing the amplitude of the detected energy after the seal has been started and prior to the sealing operation commencing. The acoustic energy has a carrier frequency that randomly varies over a relatively broad band to prevent acoustic nodes in the passageway.

Abstract: New and improved apparatus and method for seismic exploration on land transports sensing geophones with a flat, lightweight, towing medium or sheet which conforms to the earth's surface. The geophones are mounted on sleds attached to the towing medium by strips or members of resilient material which isolate and decouple the geophone from vibrations and the like induced, sensed, or transmitted by the towing medium. The resilient members enable the geophones and sleds to continually maintain contact with the earth's surface over irregularities in the surface to provide good ground coupling for more accurate seismic exploration results. Plural or multiple towing mediums may be coupled together and towed into place for use in accordance with the desired geophone array to be used.

Abstract: The current flowing through the horizontal deflection coil of a cathod ray tube is controlled by a transistor which is switched between saturation and cut off by a circuit having a pulse generator for generating a pulse in response to a horizontal synchronizing pulse. The leading edge of the generated pulse is delayed before being applied to the controlling transistor which switches sometime thereafter due to the storage time of the transistor. To insure that the blanking of the electron beam of the tube takes place during the retrace time, the blanking interval is set to occur a period of time after the horizontal synchronizing signal which is less than the sum of the storage time of the transistor and the time which the leading edge of the generated pulse is delayed.

Abstract: Glass powder is wetted with an aqueous solution or emulsion of an organic binder and mixed with carbon black in the form of soot or lampblack. The resulting material is packed between the parts of the central electrode of a sparkplug and fired at a temperature sufficient to fuse the glass to produce a gas-tight seal with electrically conducting properties. Up to 5% of metal powders may be included in the material if it is desired to prevent the resistance from rising during service. Oxides or carbides and certain other metal powders may be added to bring the thermal expansion coefficient to a desired average value.

Abstract: The detection of acoustic emissions emanating from an object is achieved with a capacitive transducer coupled to the object. The capacitive transducer is charged and then allowed to discharge with the rate of discharge being monitored. Oscillations in the rate of discharge about the normally exponential discharge curve for the capacitive transducer indicate the presence of acoustic emissions.