Abstract: A spread spectrum communication system having a plurality of transmitters at remote locations capable of transmitting information to one or more receivers during a plurality of information time durations. A message structure interposing the plurality of information time durations with a plurality of preamble time durations, during which time the receiver detects message transmission, is also provided.

Abstract: A self-calibrating ultrasonic distance sensing method and apparatus are disclosed in which a transducer periodically transmits a pair of bursts of acoustic energy along an acoustic path toward a target object. Echoes of the first acoustic burst in the burst pairs from a reference target at a known distance from the transducer are used for calibration purposes, and echoes of the second acoustic bursts in the pairs are used to determine distance to the target object.

Abstract: An ultrasonic distance sensing method and apparatus are disclosed in which a transducer periodically transmits a pair of bursts of acoustic energy along an acoustic path toward a target object, an echo of the first acoustic burst in each burst pair is used to establish a peak reference level, and an echo of the second burst in each pair is used to determine distance to the target object only if its level exceeds a predetermined fraction of the peak reference level.

Abstract: A single transducer ultrasonic target detector and detection method are disclosed which provide for detection down to substantially zero distance from the detector housing envelope with an electroacoustic transducer subject to unavoidable ringing following emission of a burst of acoustic energy. The housing is configured with a retroreflecting surface proximate the transducer so that acoustic energy reflected from the target is repeatedly reflected back toward the target until the ringing has subsided sufficiently to permit reception of the reflected acoustic energy by the transducer.

Abstract: A light energy information transmission system for transmitting digital coded information as a modulated light signal. The light energy information transmission system is preferably comprised of four remote control units each of which transmits a series of amplitude modulated infrared information pulses at a discrete frequency and a single receiver module for demodulating the information pulses received from each control unit and for transmitting the information carried thereby to a computing system. Each portable control unit includes a digital joystick which is movable in any direction in an X-Y plane and a keyboard having a plurality of keyswitches for selectively inputting the information to be transmitted. The information is then encoded as a 12-bit data word, and transmitted as a series of amplitude modulated infrared pulses which are detected by the receiver module. The infrared pulses are reconverted to electrical pulses, demodulated and transmitted to the computing system.