Abstract: A speed detector, for use with a tone wheel having metal teeth, employs two coils positioned in offset relation near the tone wheel for interacting with the tone wheel teeth and thus changing their respective inductances. The coils preferably include iron cores to enhance magnetic coupling. One coil is in a phase sense oscillator circuit and the other is an a tuned sensor network. The oscillator is coupled to, and drives, the tuned network. The change in coil inductances effects a phase shift of the resulting signals in the oscillator and the tuned network, the magnitude of that phase shift typically being double that for a comparable single coil system. The output signals of the oscillator and tuned network provide inputs to a phase condition detector which looks for a reversal in their phase sequence and uses such event to provide timing reference pulses for a final determination of speed in a known manner.

Abstract: A capacitance keyboard switch is provided which reduces in a keyboard the overall space requirements therefore while providing at the same time the property of increasing the switch module force curve in the activating movement thereof. The tactile feel construction includes a reduced number of integrally molded inexpensive parts.

Abstract: A space bar construction is provided for low profile keyboards which will accommodate, with the same construction, from a 1 to 3 space bar up to a 1 to 9 space bar. The arrangement provides a leveling system for the space bar to maintain exactly equal the depressed distances of the space bar at each end thereof through the utilization of a torsion spring for the leveling wire. The torsion spring imparts a constant loading in the leveling wire, and consequently the key top to avoid any noisy "play" between the parts. The unit is assembled complete as a self-contained module for later insertion into a low profile keyboard.

Abstract: A capacitance keyboard switch is provided which is of substantially reduced vertical dimensions for reducing in a keyboard the overall space requirements therefore. The switch of the invention has an overall height of only 0.750 inches (19.05 mm), and a length of travel of as much as 0.150 inches (3.81 mm). This is achieved by eliminating a housing for the switch altogether, utilizing a cooperating plunger-snap-in guide combination, and a single sheet movable capacitor plate which cooperates with a plate on the printed circuit board. In addition, the entire assembly is mounted and supported on the printed circuit board with the components snapped together without the use of separate hardware, such as screws or nuts.