Abstract: Apparatus and method for non-contact determination of shaft angle utilizes a patterned disc secured to the shaft or other rotor being observed. The disc has sectors of different optical properties whereby radiant energy directed to the disc will be encoded by the sectored pattern. A set of detectors, which each correspond to one of the sectors, provides variable output signals according to the amount of radiant energy attenuated by the disc and directed onto the detectors. These signals are converted to a set of digital signals which define a unique rotational position, and a computing means calculates angular position from these signals. The computing means will, if necessary, compare the digital output signals and then calculate angular position in a manner which is insensitive to small decenters (or lack of concentricity) in the arrangement of the shaft, disc, detectors, and any associated optical system.

Abstract: A tamper-proof and wear resistant identification card having a support layer, a strip of magnetic tape for containing encoded information, transparent layers covering the front and rear surfaces of the support layer and a screen of optically-readable encoded information on a surface of one of the transparent layers.

Abstract: A compact portable housing encloses a piezoelectric element which receives short pulses from a pulse generator circuit controlled by a ramping waveform generator circuit so that the element and the adjacent speaker portion of the housing produce a frequency modulated loud sweeping sound. The housing also encloses a detector switch for sensing a disturbance, and the sensitivity of the switch may be adjusted according to the position of the housing. The detector switch actuates a timer circuit which is armed or disarmed by moving a combination code switch having code wheels projecting from the housing.