Abstract: The comparator comprises a circuit for detecting the sign of the phase-shift of the reference signal relatively to the second signal for a predetermined phase of the latter. It delivers a corresponding binary phase difference signal.A second circuit selects those changes in values of the phase difference signal which occur for a phase of the reference signal comprised in a predetermined phase interval, and are thus surely representative of a change in the sign of the frequency difference.

Abstract: Circuits and auxiliary elements for use with a device for controlling the emission of light pulses from a flash unit, which light pulses are produced by the discharge of current pulses from a capacitor, the device including a light sensing element for receiving light produced by the flash unit and reflected from an object in the light path. One such circuit includes two zener diodes for providing threshold voltages for use in comparing the output of the light sensing element. Another such circuit compensates for nonlinearities in the response of certain components of the device.

Abstract: Method and apparatus are described for reducing amplifier distortion by establishing a first signal at a first frequency to be amplified in an amplifier which while amplifying the first signal produces a second undesired signal at another frequency, producing on a cycle by cycle basis of the first signal a third signal at the other frequency, adjusting by no more than substantially 180.degree. the relative phase and amplitude of the first and third signals for mutual cancellation of the second and third signals and then amplifying the first signal in the amplifier and reducing the power of signals at the other frequency relative to the power of the amplifier signal at the first frequency. Examples are given where the second signal is a harmonic or an intermodulation frequency signal of the first signal.

Abstract: An ionization smoke detector having two ionization chambers with one of said chambers having an electrode at least partially surrounded by a conductive mesh constituting an intermediate electrode and the other of said chambers being formed between the intermediate electrode and an outer surrounding electrode of conductive mesh and a radioactive source carried by said outer electrode. The volume defined by the outer and intermediate electrodes is greater than the volume defined by the intermediate electrode.

Abstract: A ballast especially useful in forming symmetrical half cycles of lamp current during dim light level operation, and thus in overcomming a type of lamp flicker. The light level of the lamp is controlled by an intensity selector circuit which controls an auxiliary circuit that, in turn, controls the ballast circuit. The intensity selector circuit comprises an oscillator which produces timing pulses at a frequency controlled by a potentiometer. The oscillator operates a control switch in the auxiliary circuit and the control switch supplies gate current for a power switch. The power switch controls the ballast circuit which turns on the lamp during a portion of each current half cycle; the light level being determined by the length of the conduction portion of that half cycle. The ballast circuit comprises primary, secondary, and heating windings mounted on a common core. The primary winding is connected to ground through a resistor.

Abstract: In an ophthalmometer comprising a chart plate, an illuminating device for illuminating the chart plate, a viewing optical system having an optical measurement adjust member for viewing therethrough the chart image projected by the illuminating device upon the cornea of an eye to be examined, a scale read-out device movable with the optical member and having a cornea curvature radius scale plate, and an astigmatism axis angle scale plate, the illuminating device comprises a chart illuminating light source member disposed behind the chart and within the viewing optical system and being in an annular form corresponding to the configuration of the chart of the chart plate. The illuminating device further includes a reflector member having light-transmitting portions for directing therethrough light beams for illuminating the two scale plates, respectively.

Abstract: The noise in a crossed field amplifier output is reduced by providing a non-uniform magnetic field across the surface of the cathode. This may be achieved by providing a curved magnetic field across the cathode or by providing a concave shaped cathode. Additionally the cathode may be tilted with respect to the cross magnetic field.

Abstract: A wideband differential amplifier comprises a pair of differentially connected control devices, for example transistors, having a pair of semiconductor junction input devices coupled thereto for receiving complementary input currents. The input devices exhibit logarithmic characteristics substantially compensating for nonlinear properties of the pair of differentially connected control devices, whereby a linear rather than a nonlinear amplified current output is produced. Multipliers, cascaded amplifiers, and other useful circuit configurations are provided.