Abstract: The modal-insensitive coupler consists of a number N of optical multimode fiber lengths, each fiber length having a core of initial predetermined cross-sectional area. The fiber lengths are fused together in a coupling section such that the cores of the fiber lengths have a reduced cross-sectional area in the coupling section which supports a minimum number of modes of optical energy at a predetermined wavelength, and such that the fiber lengths have different core cross-sectional areas to produce preselected coupling ratios.

Abstract: The battery current switch includes an opto-isolated switch which is controlled to open when the battery voltage falls below a predetermined voltage and/or when the battery load current goes above a predetermined current level.

Abstract: The apparatus includes a frequency selective memory having a storage material for storing frequency holes in at least two spatial dimensions and a frequency dimension. Interference patterns are stored in the memory such that each complete interference pattern is found in the spatial dimensions while the series of interference patterns is in the frequency dimension. A laser beam is directed onto the surface of the memory to read the memory. By changing the electric field across the storage material, subsequent interference patterns are shifted in the frequency dimension into resonance with the laser beam thereby changing the interference pattern detected. The interference patterns may be a series of holographic interference patterns which would provide as an output a series of three dimensional images, or they may be a series of gratings which would provide a laser beam which scans in a spatial dimension as an output.

Abstract: The commutation circuit for commutating a conducting thyristor includes an inductance, a capacitance and a commutation thyristor all connected in series with the conducting thyristor and the dc source, the commutation thyristor initiates the commutation when triggered. The circuit further includes a first diode connected in reverse polarity across the commutation thyristor and a second diode connected in reverse polarity across the commutation thyristor-capacitance series circuit. The voltage across the capacitance is zero when each commutation cycle is initiated, and also when each commutation cycle ends.

Abstract: In a solar system collector loop, having a solar collector with an absorber plate, a heat storage unit and a pump for circulating a fluid between the collector and the storage unit, the stagnation temperature T.sub.Q of the collector absorber plate, the temperature T.sub.C of the collector absorber plate, and the storage temperature T.sub.S in the storage unit are measured. The stagnation temperature is measured by a heat flux transducer based on a small sample of the absorbed plate which is thermally isolated from the collector but in the same enclosure. This transducer generates temperatures near the stagnation condition for the instantaneous operating point. In the method of control, the pump is turned on when the temperature difference between the absorber plate T.sub.C or T.sub.Q and the storage T.sub.S, is greater than a predetermined value T.sub.on. The pump is turned off when the temperature difference between the stagnation temperature T.sub.Q and collector absorber plate T.sub.

Abstract: The timed AC switch comprises a manual on-off switch in series with bidirectional semiconductor switch, such as a triac, for connection in a loop with an AC source and a load which would generally be incandescent or fluorescent lamps. The semiconductor switch is driven by an RC oscillator which is under the control of an inhibit circuit and a digital counter which itself is driven by the oscillator. The counter is reset at initial start up, and may also be reset while operating or after counting out. The times switch may also be controlled to inhibit the oscillator for a very short time as a warning before finally timing out.

Abstract: The optoelectronic switch includes a photosensitive GaAs FET onto which an optical signal may be directed. The optical signal is derived from an RF modulated light source. A voltage circuit is connected to the FET to switch the FET "on" or "off" by placing a positive or zero voltage respectively on the drain. An isolation of over 70 dB is obtained in this FET switch.

Abstract: The jitter determining apparatus uses only a jittery clock signal of period T.sub.b recovered from the received data signal to determine peak to peak jitter J.sub.pp and jitter distribution. The apparatus includes an AND gate having a pair of inputs. The inputs are coupled to a first signal which is the jittery clock signal delayed by a fixed amount nT.sub.b where n is preferably greater than 5, and to a second signal which is a jittery pulse signal generated from the jittery clock signal. The second signal is also controllably delayed by a factor greater than twice the jitter J.sub.pp. The AND gate produces output pulses when coincidence occurs between the two signals as the delay of the second signal is selectively varied. A counter counts the pulses for each selected delay position and thus provides the peak to peak time jitter J.sub.pp of the clock signal.

Abstract: The microwave heating apparatus consists of a microwave cavity, a energizing source, a mechanism for holding and agitating a load, and a temperature detector for continuously monitoring the temperature of the load. It is particularly useful for heating and quickly thawing frozen blood plasma or intravenous admixtures as needed. These must be thawed uniformly and to some preselected temperature so as not to destroy their effectiveness. It also helps to prevent wastage of the blood plasma thawed in anticipation of an emergency.

Abstract: The apparatus generates two optical beams which are directed to a relatively moving solid surface where an interference pattern, having substantially parallel fringes, is formed. The light is scattered and thereby modulated by irregularities on the surface. This modulated light is received and the signal is processed to indicate the length of the surface or its relative speed. The signal processor converts the modulated light signal to a pulse train, and adds pulses to the pulse train when a drop-out in the signal is detected, i.e. when the time between pulses in the pulse train is greater than a factor times the average period of the pulse train. The corrected pulse train is a function of the length of the surface or the relative motion between the apparatus and the surface.

Abstract: The ac current comparator bridge measures the resistance of an unknown resistor at 50-60 Hz with an accuracy in the order of 10 parts per million. The current in the unknown resistor is compared, using a current comparator, to the current in a reference resistor for the in-phase component, and to the current in a reference capacitor for the quadrature component or phase defect. Once an ampere-turn balance is achieved in the comparator by adjusting the winding turns, the unknown resistor's values are a function of the reference resistor, the reference capacitor, the voltage sources driving the currents through the unknown resistor and the references, as well as the turns of the windings.

Abstract: The multi-filar moving coil loudspeaker includes a magnetic field structure which provides a unidirectional magnetic flux across an air gap, an acoustic diaphragm, and a coil set positioned in the air gap and connected to the diaphragm. The coil set has a plurality of insulated coils wherein the coils have approximately the same resistance and inductance and cut substantially the same flux lines in the air gap. The coil set has two or more wires which are twisted around one another and then wound about a coil form. The coils in the coil set may be connected in series or parallel aiding, or in series bucking pairs. In a loudspeaker circuit, the coils are connected into two groups, each having one or more coils. The first group is connected to input terminals, and the second group is connected to a feedback amplifier having an output connected to the first group of coils.

Abstract: A cathode structure for gas lasers comprising a flat plate of non-conducting material positioned in the laser in spaced relation to the laser anode to define a discharge region therebetween, a two-dimensional array of metal sub-electrode rods passing through the plate and having their upper ends lying flush with the surface of the plate, a block of dielectric material positioned below the plate and containing a series of transverse channels therein, electric current conductors lying in the channels and adapted for connection to a power supply, the lower ends of the said rods passing through openings in the block into the channels to define a predetermined uniform gap between the ends of the rods and the electrical conductor, and a liquid electrolyte solution filling the channels and electrically connecting the sub-electrode rods and the conductors.