Abstract: A distributed acoustic sensor utilizing a Fizeau type fiber optic transducer and a distributed acoustic collector to gather and return acoustic disturbances from remote areas in buried, underground, or underwater installations. A light beam from a laser or LED source is transmitted over a fiber to a remote transducer which is coupled to a distributed acoustic collector. The collector may be an extended pipe or tube system filled with an acoustic conducting medium such as air or an appropriate liquid which communicates with the sensing diaphragm in the transducer. An interference beam whose characteristics are a function of the diaphragm motion is created in the transducer and transmitted back over the common single fiber toward the source. An in-line optical coupler/splitter diverts a portion of the returning modulated beam to a photodetector which outputs a proportional electrical signal to an electronic circuit for amplification and analysis.

Abstract: A motor driven vertically adjustable work surface or desk which is optimized to support a substantial load of equipment cantilevered toward the front of the surface. The work surface is supported by a pair of motor driven telescoping legs having internal rolling bearings and rack and pinion drive arranged to eliminate sliding friction and maintain smooth motion. The telescoping legs are mounted toward the rear of the work surface and supported on a base or wall so as to provide maximum clearance under the front of the desk to accommodate wheelchairs and the like.

Abstract: A distributed fiber optic sensing system for detecting mechanical, acoustic, or ultrasonic disturbances is disclosed. This system is optimized for use as an intrusion detection system in security applications. Light is launched into opposite ends of a sensing fiber loop such that two beams circulate through the loop in opposite directions and then recombine to produce an interference pattern on a photoelectric detector. Disturbances of the sensing fiber loop produce corresponding changes in the interference pattern and thereby the signal level at the detecter. The changes in the electrical signal from the detector are interpreted to provide alarms when the sensing fiber loop is impinged upon by intrusive disturbances, and to provide location of disturbances along the loop. Means are incorporated to decode uniquely coded sonic or ultrasonic signals from personal transmitters borne by authorized personnel approaching the sensing fiber loop.