Abstract: A stepping motor is simulated by controlling the orientation of a servomotor's shaft with a control feedback circuit that generates a control signal based upon signals from an optical shaft encoder. The encoder includes a rotary light mask having symmetrically arranged transparent and opaque regions which move across the axes of paired, fixed, optical channels. The two channels of each pair are angularly disposed around the axis of the light mask such that, whenever the light fluxes striking both channels' detectors are changing, one will be increasing and the other decreasing. The analog control signal is generated as the difference of the voltage outputs of paired detectors.

Abstract: An ultrasonic nondestructive testing system and a "sled" for use in such a system are provided for nondestructively inspecting a workpiece. The "sled" includes an ultrasonic search unit effective to radiate or transmit ultrasonic energy in response to a driving signal and to receive ultrasonic energy and produce a received signal corresponding to the incident ultrasonic energy. The sled includes a sealed chamber filled with a liquid couplant. A resilient, elastomeric diaphragm forms one side of the chamber and is adapted to slide along the surface of the workpiece. An ultrasonic search unit projects into the chamber so as to be acoustically coupled to the diaphragm. In addition, an elastomeric member having a high acoustical attenuation and an acoustical impedance corresponding to that of the liquid couplant is provided inside of the chamber for absorbing spurious ultrasonic energy.

Abstract: A system for detecting and counting entry and exit of passengers. Transmitted high frequency sound beams define at least two zones through which passengers pass in sequence when entering or leaving a vehicle; the motion of a passenger through the zones produces signals at a receiver which are fed to logic circuits to produce appropriate counts. The logic circuits discriminate between moving human targets and other moving objects within the zones, and include range discrimination to prevent interference from outside the detection area. In one embodiment the sensor is located above the entry area to detect passengers' heads, while another embodiment is located at a level to detect passenger foot motion.

Abstract: A system for sensing by ultrasonic vibrational energy the shape and character of objects immersed in a visually opaque transmission medium is disclosed. Frequency modulated ultrasonic waves are projected to irradiate an object, with reflected energy from scattering points on the object being imaged on an ultrasonic image camera. The camera converts the received ultrasonic image to an electronic image which is electronically scanned to produce an output video signal having an amplitude and frequency which is a linear representation of the point-by-point interrogation of the image. The video signal is fed in parallel to an amplitude modulation detector, which produces a linear signal representing the video signal envelope, and a frequency modulation detector, which produces a constant amplitude reproduction of the original modulation signal, except for shifts in phase in accordance with the time delays of reflected ultrasonic signals reaching successive image points on the camera.

Abstract: An intrusion detector operating with electromagnetic sensors to detect intruder motion within large, defined areas is disclosed. The system provides an acceptably low false alarm rate by means of range discrimination whereby moving objects outside the protected area do not affect the system and by improving sensitivity to slow-moving targets even when located very close to the sensor location. The system incorporates a transmitter which is frequency modulated by a triangular or sawtooth wave and a receiver which produces an output signal that varies in accordance with the instantaneous difference between the transmitted and received frequencies. The frequency of this difference signal is the beat frequency, and is proportional to the range of the target. Storage means are provided to permit comparison of successively received signals over a predetermined period of time, and this comparison serves to reveal slowly varying changes in the return signal pattern.

Abstract: An ultrasonic non-destructive testing system is disclosed wherein electrical signals from a search unit are displayed to visually represent reflections of ultrasonic waves occurring within a work piece or test material. The system includes means for generating an alarm or warning signal informing the operator that an ultrasonic echo has occurred which indicates a possible defect. The alarm causes the display screen to be flashed "on" and "off" at a slow rate in response to a detected ultrasonic echo which exceeds the critical level. The flashing screen signals the operator to make a closer visual inspection of the display, which appears intermittently as the display is flashed on and off.

Abstract: An ultrasonic nondestructive testing system and a contact-type, ultrasonic search unit for use in connection therewith are disclosed. The ultrasonic search unit includes a transducer crystal for receiving and transmitting ultrasonic energy, a housing in which the crystal is mounted, a dampening backing compound, and a wear-resistant cylindrical member or ring disposed within the housing and in which the crystal is mounted to provide a hard, durable, long-lasting contact face.