Abstract: Gas discharge lamps may conduct current from the common rail to earthen ground through a fixture containing the lamps. A transistor is coupled in series in the current path to the common rail. When the ballast is placed in a quiescent state, the transistor is rendered non-conducting, thereby solating the lamps from the common rail and preventing flicker. In accordance with another aspect of the invention, the control electrode of the transistor is coupled to a source of low voltage and the transistor is rendered non-conducting when the source of low voltage is turned off. The lamps can also be isolated from the common rail by using a semiconductor switch in the rectifier section or by referencing the output of the inverter to the high voltage rail.

Abstract: Apparatus and methods are provided for sensing the presence of bright white paper on a conveyor of a paper sorting system. The conveyor is constantly illuminated with ultraviolet light. When bright white paper is present in the inspection zone of the conveyor, it will re-radiate fluorescent light energy as a result of the ultraviolet light. Periodically, the inspection zone of the conveyor is illuminated with a second light source in the visible light spectrum. Light is collected from the inspection zone of the conveyor, including reflected light from the secondary source and including emitted fluorescent light energy as a result of the ultraviolet light falling on bright white paper. Periodically a microprocessor associated with the sensor senses reflected light from the second source to determine whether any object if present on the conveyor. The microprocessor then senses the level of fluorescent light energy being emitted from any object on the conveyor.

Abstract: A transducer for detecting vibrations in an object. Multiple pickup coils are utilized which are sensitive to both the vibrations in the string plane and the vibrations perpendicular to the string plane. This system subtracts the signals from the first and second pickups to create a signal representing the vibrations in the string plane and combines the signals from the first pickup and the second pickup for determining the string vibrations perpendicular to the string plane. In one embodiment of the invention, the transducer uses one pole of the pickup as a bridge saddle for supporting the guitar string. The saddle pole of the pickup is constructed from a magnetically permeable material. The saddle pole causes the lines of magnetic flux to be carried in large part by the guitar string and allows for a reduction in the total magnetic energy requirement for the pickup's permanent magnet to reduce the cross talk between adjacent string sensors within a polyphonic pickup.