Abstract: A frequency-agile source of microwave frequency signals is shown to include: a voltage-controlled oscillator operating within a band of microwave frequencies; a crystal-controlled oscillator operating at a frequency lower than the band of microwave frequencies and producing harmonics within such band; a phase detector having samples of the signals out of the crystal-controlled oscillator and the voltage-controlled oscillator applied as input signals; and a shaping amplifier receiving the output signal of the phase detector to provide a control signal related to the phase difference between the signal out of the voltage-controlled oscillator and the harmonic of the crystal-controlled oscillator nearest to the frequency of the voltage-controlled oscillator.

Abstract: A radar transmitter is shown to include a voltage-controlled oscillator and associated amplifier to produce a signal to be transmitted with any noise generated within such oscillator and amplifier being reduced to a minimum by extracting a sample of the signal to be transmitted, downconverting such sample and then phase detecting the downconverted sample to derive a control signal for such oscillator.

Abstract: In a control circuit for a voltage-controlled oscillator including the combination of: (a) a source of D.C. power, the voltage out of such source being adjustable in discrete steps to provide a coarse frequency control signal; (b) a control loop, responsive to the signal out of the voltage-controlled oscillator, to provide a fine frequency control signal; and (c) a summer to combine the coarse and fine frequency control signals into a single frequency control signal for the voltage-controlled oscillator, an improvement is shown wherein the control loop comprises an interferometer wherein noise extant on the signal out of the voltage-controlled oscillator is degenerated by dividing a portion of such signal into a reference path, a delayed path and a parallel path, the signals in the latter two paths being processed to produce an amplitude corrected signal for combination with the signal, shifted by 90.degree., in the reference path, finally to produce the fine frequency control signal.

Abstract: A radiation shadow indicator having a sight tube for sighting shadow-casting objects along a sighting axis. The indicator includes a system of gimbals mounting the tube for angular movement so that the sighting axis thereof may be caused to follow the apparent diurnal movement of celestial objects at various seasons of the year. Position indicators are provided for instantaneous read-out of angular positions of the gimbal device which, in turn, correspond to positions of the sighting axis at given seasons and/or times of day in relation to the location of the indicator on the surface of the earth.

Abstract: A coal-shale interface detection system for use with coal cutting equipment consisting of a reciprocating hammer having an accelerometer mounted thereon to measure the impact of the hammer as it penetrates the ceiling or floor surface of a mine. Additionally, a pair of reflectometers simultaneously view the same surface, and the outputs from the accelerometer and reflectometers are detected and jointly registered to determine when an interface between coal and shale is being cut through.

Abstract: A measurement system for measuring the departures from a straight line of discrete track sections of a track along a coal face in a mine employing a vehicle having a pair of spaced wheel assemblies which align with the track. A reference arm pivotally connects between the wheel assemblies, and there is indicating means for measuring the angle of pivot between the arm and each of the wheel assemblies. The length of the device is less than the length of a track section, and thus when one of the wheel assemblies is on one track section and one is on an adjoining track section, the sum of the indicated angles will be indicative of the angle between track sections. Thus, from the length of a track section and angle, the departure of each track section from the line may be calculated.

Abstract: What follows is a description of a three track mechanism assembly for a vehicle door, and in particular for a light rail vehicle door. Each track mechanism includes a guide rail for guiding the door in its opening and closing movement relative to the vehicle body. Two of the track mechanisms include actuators for producing the opening and closing movement of the door. One of these actuators produces the desired longitudinal displacement of the door relative to the vehicle body, while the other actuator produces the desired transverse displacement of the door relative to the vehicle body. In addition, an extraction device can be included with the track mechanism having the actuator producing the desired longitudinal displacement for assisting the other actuator in producing the desired transverse displacement of the door relative to the vehicle body.

Abstract: An input signal, whose frequency is to be detected, is divided and sent i two arms. One arm applies a set phase and amplitude adjustment while the other arm has a phase response that is dependent upon the frequency. Both arms are fed to a phase detector whose output is used to indicate the frequency of the input.