Abstract: A construction for compact catapults is described. An elastic cord is mounted and placed in tension by threading it through a number of grooved reels. The reels are rotatably fastened to capstans and thereby to a handle-equipped base. When a U-shaped pellet is hooked over a portion of the elastic cord, drawn back and then released, high acceleration forces are transferred to the pellet which then issues from the catapult.

Abstract: A detector apparatus for counterfeit paper currency comprising a clamp and torsion pendulum assembly for holding a note to be tested, a moveable magnetic field source mounted so that it can be brought into contact with the note and then withdrawn, and indicating means for detecting and measuring deflection of the note.

Abstract: A level sensing system for fluids and particulate material comprised of an immersed rotating body, an arrangement for measuring the resistance to rotation encountered by said body and a compensating method for reducing the effect of extraneous variables whereby said resistance varies primarily with changes in level. Output devices and controls attached to read and act from said resistance measurements can thus be calibrated in terms of fluid and particulate material levels in various storage vessels.