Abstract: A manual data entry keyboard includes a plurality of key assemblies, each having an elongated arm and a touch contact at an outer end region of a respective arm. The arms are movable between a retracted position and an extended position, in the latter of which the touch contacts are spaced apart from each other by distances sufficient to enable a user to engage one touch contact at a time without simultaneously engaging an adjacent touch contact. A synchronizer ring simultaneously moves all of the arms between the retracted and extended positions.

Abstract: A fail-safe voltage-limiting circuit for an audio frequency-controlled railway track circuit includes a pair of NPN transistors arranged in the manner of a darlington pair, wherein the base connector of the first transistor receives an amplitude-modulated signal from a filter and detector circuit connected to the rails. A first pair of resistors arranged in series between the positive and negative system battery lines, includes a first fail-safe resistors also connected to the collector of the first transistor. The ratio of the first and second resistors are selected to limit the positive excursion of the input signal, thus clipping excess noise at this limit. A second pair of resistors is coupled to the second transistor to limit the negative excursion of the amplitude-modulated input signal. The second pair of resistors includes a second fail-safe resistor connected to the emitter of the second transistor and a third resistor connected in series to the second fail-safe resistor at this junction as well.

Abstract: A battery monitor circuit for rechargeable multicell batteries that provides a reliable indication of battery failure independent of temperature, load and age, by continuously comparing the impedance of the cells of the battery against each other. Comparison means are provided responsive to a first voltage at a tapped terminal of the battery that divides the battery cells into two groups, and to a second voltage that represents a fraction of the battery voltage corresponding to the ratio of the number of cells in each group, said comparison means generating an error signal when said first and second voltages change so as to experience a reversal in relative magnitude, which is indicative of cell deterioration.

Abstract: A retractable roof top sign for automotive vehicles including a generally rectangular low profile frame for attachment to the roof of the vehicle and a sign structure transversely spanning the frame in pivotal attachment at a lower end between a pair of longitudinal side rails of the frame, a small gear motor being provided in driving connection to the sign in a manner so as to permit the sign to be selectively moved between a retracted position within the confines of the frame and a vertically erect position by operation of appropriate electric control switches mounted in the operator's compartment of the vehicle. For use in police cruisers or the like, an attention getting light flasher bar extends across the top width of the sign, and front an rear lights mounted within the confines of the frame are directed respectively on front and back messages displayed on the sign.

Abstract: A passive electromagnetically responsive device comprising a miniature tuned inductive-capacitive circuit. The device is preferably detected by stimulating oscillations at the resonant frequency of the circuit by a pulsed electromagnetic field. The device is desirably used in projectiles to enable remote tagging and detection and/or identification of livestock.