Abstract: The apparatus comprises a wire sheet graphics tablet and a display apparatus, particularly a cathode ray tube, for receiving the signals transmitted by the graphics tablet. Alternating current flows through wires (5,6) of the tablet. The non-conducting plate (4) of the tablet is transparent and the wire sheets (5,6) are made up of transparent electrical conductors or of small conducting wires, which makes them practically invisible. The tablet is placed on the screen of the display apparatus. Between the screen of the cathode ray tube and the lower side of the graphics tablet, a transparent conducting and non-magnetic coating (8) is provided. In one variation, the current flowing through the layers of wire (5,6) is a high frequency current. The pen for the graphics tablet may be a metallic rod covered by a sheath of insulating material.

Abstract: A modulator for monochromatic beam of radiation, such as a laser beam, consists of a semiconductor crystal body. A sufficient potential is applied to the body to produce a moving zone of resistivity and potential gradient varying from the remainder of the body. The zone may result, for example, from the Gunn effect or the piezoelectric effect. The zone also has optical properties differing from the remainder of the body, so that a beam directed at the crystal can be modulated by the moving zone.