Abstract: Disclosed is an electronic integral drafting instrument which measures its own linear displacement and displays any desired multiple or submultiple of the actual displacement. The instrument includes a straightedged plate which houses: a displacement sensor with a driving wheel which projects beneath the plate, an electronic up-down counter and calculator type circuit, a scale factor keyboard, an electronic digital display, and a sensor which detects and annunciates if the displacement sensor driving wheel does not make proper contact with the drawing media. One embodiment of the invention is easily attached to conventional drafting machines as a replacement for regular straightedges and scales. A second embodiment of the invention may be used without a drafting machine. The leading straightedge of the instrument can be lifted or lowered into contact with the drawing media. An extension straightedge may be attached to the leading edge of the instrument.

Abstract: An apparatus is provided for controlling the activation of a high energy radiation source having a shutter. The apparatus includes magnets and magnetically responsive switches appropriately placed and interconnected so that only with the shutter and other parts of the source in proper position can safe emission of radiation out an open shutter occur.