Abstract: A fluid level sensor comprising a novel electronic circuit which monitors change in the fluid level in a reservoir through a conductive probe disposed therein. The probe and a capacitor are electrically connected in a circuit which is intermittently energized to create an electrical transient therein. The transient is monitored, and a warning is given when the transient indicates that the probe is not in contact with the fluid in the reservoir. Two embodiments are disclosed as applied to a vehicle hydraulic brake system having a dual reservoir type master brake cylinder with a probe for each reservoir. In one, only a single capacitor is required since the electronic circuit electrically connects each probe with the capacitor sequentially by means of time multiplexing. In the other, a capacitor is required for each probe and the transients in each capacitor/probe circuit are fed to a logic circuit which determines if any of the probes is out of contact with the fluid in the reservoir.

Abstract: A modulator for modulating an audio signal in response to a dc signal of adjustable level and concurrently in response to a sub-audio signal, in which the modulating signals do not appear in the output of the modulator nor intermodulate each other, the system including transistor pairs which respond differentially at the bases to the modulating signal and additively to the audio signal in response to application of the audio signal at the emitters.

Abstract: A digital FSK time rate change modulator is responsive to a digital input signal and generates either a first or a second output frequency. The FSK modulator switches from one output frequency to the other in small increments over a predetermined time interval. The FSK modulator includes means for generating a first and a second timing signal and input means for receiving the digital input signal. An up-down counter having an up-count input and a down-count input counts up and down between a first and a second state. First gating means is coupled to the output of the up-down counter and to the input means and passes the second timing signal to the up-count input when a high level digital input signal is present on the input means and the up-down counter is not in the second state.

Abstract: An electrodeless lamp is excited by high frequency power in a termination fixture having an inner and an outer conductor, the lamp being located in the high field region at the end of the conductors. A source of ultraviolet radiation is located near the lamp and is activated momentarily when the lamp is to be excited. The radiation assists in initiating breakdown and excitation of the fill material in the lamp.

Abstract: An amplitude limiting amplifier followed by a filter network is interposed between the voltage amplification stage and the impedance matching stage in a Butler oscillator. This allows both the voltage amplification stage and the impedance matching stage to be operated in a linear mode at all times which assures that a piezoelectric crystal connected between the stages is connected in a relatively low, constant impedance path and is driven by a sinusoidal waveform, free of distortion, to assure maximum frequency stability.

Abstract: An injection laser, whose sides are chemically etched to produce facing 45.degree. mirrors, can be made to emit lasing light in the same direction as current going through the p-n junction. A two dimensional array of lasers is produced wherein the location of each laser is uniformly spaced from an adjacent laser.

Abstract: An improved semiconductor and semiconductor coating for alumina electrical insulating devices is disclosed. The semiconductor is prepared by applying a layer of a mixture of monoxide and sesquioxide combination to an alumina body and firing at a temperature of 2300.degree. or above thereby forming a stable spinel. The electrically-conductive monoxide can be FeO, Cu.sub.2 O, CuO, NiO, CoO or MnO. The sesquioxide can be Fe.sub.2 O.sub.3, Cr.sub.2 O.sub.3, Ga.sub.2 O.sub.3, Ca.sub.2 O.sub.3, Mn.sub.2 O.sub.3, Al.sub.2 O.sub.3 or Ti.sub.2 O.sub.3.

Abstract: An integrated circuit oscillator includes a timing circuit and a bistable circuit for controlling the timing circuit. The timing circuit includes a capacitor and a pair of field effect transistors (FET), one of which is employed for charging the capacitor and the other of which is employed for discharging the capacitor. A first stage having a relatively low trip voltage is responsive to a low level of charge on the capacitor for actuating the bistable circuit to a first state and a second stage having a relatively high trip voltage is responsive to a high level of charge on the capacitor for actuating the bistable circuit to a second state. The charging and discharging FET's are rendered conductive in response to the first and second states, respectively, of the bistable circuit, such that the capacitor is both charged and discharged over relatively long time periods.

Abstract: The invention relates to a low pressure sodium vapor discharge lamp for generating a directed light beam in which the lamp is provided with a cylindrical discharge tube which is enveloped by a cylindrical outer bulb.According to the invention the inside of the outer bulb is provided, in a cross-section of the lamp over at least 270.degree. of arc, with a reflecting layer which has a large reflection factor for sodium light and a very small reflection factor for infra-red radiation.The lamp according to the invention may for example be used in an exposure apparatus for photocopying texts and figures.

Abstract: A termination fixture for an electrodeless lamp has dimensions which match the output impedance of a coupled high frequency power source to the real impedance of the lamp when in a discharge condition. The fixture may consist of a pair of coaxial conductors, and the lamp forms the termination load for the ends of the conductors. The length of the conductors is such as to place the lamp one quarter wavelength from the opposite ends of the conductors. The diameters of the conductors are such as to produce a fixture characteristic impedance which matches the lamp impedance to the source output impedance.

Abstract: A system for demodulating digital phase-modulated wave having signal elements of constant length by detecting in a detector the signal wave elements during every period of substantially the constant length, in which a combining circuit is further provided for estimating digital information content of the signal wave elements by the use of a combined output of detected results obtained by sequentially detecting, the information content of successive two of each signal wave element of the detected output of the detector, so that a demodulated output is obtained by selecting one of the outputs of the detector or the combining circuit.

Abstract: A precision test frequency generator capable of selectively providing a sinusoidal output wave within a frequency range simulating the output of a flowmeter yielding a sinusoidal signal whose frequency is proportional to flow rate, the signal having a noise component superimposed thereon. The generator is constituted by a stable high-frequency standard coupled to a selectable output counter providing intermediate-frequency pulses whose repetition rate is a sub-multiple of the high-frequency standard and a predetermined multiple of the desired output frequency of the generator. The pulses are converted into a triangular wave whose frequency corresponds to the desired output frequency, the triangular wave having a staircase formation whose number of steps is determined by the multiple. The triangular wave is converted into a sinusoidal wave of the same frequency with a staircase modulation component simulating the flowmeter output signal.

Abstract: An improved balanced dual output diode mixer circuit having separate output terminals for audio and RF output signals is disclosed. The mixer circuit includes a first transformer having a primary and a center tapped secondary winding. The ends of the secondary winding are coupled to end terminals of two separate secondary windings of a second transformer through a switching circuit which comprises four diodes. RF bypass capacitors are coupled between an RF terminal and end terminals of the secondary windings of the second transformer and provide a low RF and a high audio impedance therebetween. RF chokes are coupled between audio output terminals and the RF bypass capacitors and provide a low impedance audio path which is connected at a point of low RF impedance. A pair of resistors coupled between ground and the RF bypass capacitors provide a DC current path to ground for the rectified DC current created by the switching network.

Abstract: An oscillation frequency control device which comprises a voltage control local oscillator; a generator for giving forth an output having a predetermined referential frequency; means for periodically generating a gate pulse whose time width is equal to an integral multiple of the period of an output signal from said generator; a gate circuit for permitting the passage of an output signal from the local oscillator only during the time width of said gate pulse, wherein, while the local oscillator continues oscillation at a desired frequency, the number k of waves running through the gate circuit is chosen to be equal to an integral multiple of the counting capacity or the scale type n of a counter; said n-scale counter counts signals which have traveled through the gate circuit in at least one cycle for each supply period of the gate pulse, starting with the prescribed count at which said counter is initially reset; a count obtained in the final cycle is changed into an analog signal; comparison is made between

Abstract: Phaselock circuitry including means for providing a frequency variable feedback signal and a phase detector receiving the input signal and the feedback signal. The phase detector provides pulses whose width and average value are dependent on the phase relationship between the input and feedback signals.

Abstract: Disclosed is a Differential Phase Shift Keying demodulator employing a Hjlbert filter. Filtered and unfiltered signals are sampled at the symbol rate of an incoming signal, and the sampled signals are each applied to a delay element having a one-symbol period delay. The delayed and the undelayed replicas of the two sampled signals are linearly combined to form the demodulator's output signals.

Abstract: Phase detectors in quadrature whose outputs are simultaneously coupled to: high pass networks and cross coupled multipliers with the output summed to produce a signal proportional to the frequency difference of the signals applied to the aforesaid phase detectors; and, multipliers arranged to square the output of each phase detector whose outputs are summed to produce a signal proportional to the square of the product of the amplitudes of the signals applied to the aforesaid phase detectors.

Abstract: A variable frequency VHF or UHF band oscillator is disclosed. Principal control over the precise location and stability of the frequency of oscillation is provided by a surface wave delay line in the regenerative feedback path of a broadband amplifier. The surface wave delay line is capable of passing substantial energy within each of a plurality of very narrow passbands. Controls are provided for ensuring that at any given time the circuit can oscillate only at the resonant frequency of one of these passbands. Selection of the frequency of oscillation is in accordance with an externally applied digital frequency select signal.

Abstract: Method and apparatus for demodulating binary-phase modulated signals recorded on a magnetic stripe on a card as the card is manually inserted into a card reader. Magnetic transitions are sensed as the card is read and the time interval between immediately preceeding basic transitions determines the duration of a data sampling pulse which detects the presence or absence of an intermediate transition pulse indicative of two respective logic states. The duration of the data sampling pulse is approximately 75 percent of the preceeding interval between basic transitions to permit tracking succeeding time differences in basic transition intervals of up to approximately 25 percent.

Abstract: A device for monitoring the electrical conductivity of an electrically conductive fluid comprising at least two electrical coils for immersion in the fluid. One of the coils constitutes a coil to be energized with an alternating current and the other in use constitutes a detection coil. The coils are arranged relative to one another so that in use they are mutually inductively coupled and are inductively coupled by the fluid.An electronic circuit is provided which includes a power supply for supplying an alternating current to the coil or coils to be energized, and a detector for detecting the voltage induced in the detection coil or coils. The detector provides an indication of changes in the inductive coupling between the coil or coils to be energized and the detection coil or coils.