Abstract: An opto-electronic transducer for determining position and/or velocity of one member with respect to another member is provided with light amplitude control. The transducer is comprised of a scale with a transmission grating on a first track and an indexing bar near each end of a second track adjacent the first, and a reticle with two sections of the same grating, one section being offset spatially one quarter cycle with respect to the other section for producing quadrature signals through two photosensors opposite the first track from which relative position and/or velocity between the reticle and the scale can be determined. A slit is provided in the reticle in order to provide information for determining position relative to the indexing bars. A single photosensor opposite the second track is used both to detect the indexing bars and to provide a feedback control signal to maintain the amplitude of light illuminating the scale and reticle constant.

Abstract: A simple and compact tool for use with aircraft spark plugs to reset the spark gap, which enables a person to hold the spark plug to the tool, hold a gauge to the spark plug, and squeeze the electrodes of the spark plug to set the gap, all under field conditions. The tool includes a pair of bars pivotally connected at one end and a nut fixed to a first of the bars to loosely hold a spark plug, the nut having a cut-away portion to permit the second bar to move over a spark plug held by the nut, and the second bar having a recessed edge which can move against an electrode of the spark plug to bend it.