Abstract: An acoustic keyboard comprises a plurality of keys arranged in a matrix. A plurality of reflector members, each one associated with a different one of the keys, reflect acoustic energy when the associated key is actuated. Acoustic energy is emitted from a transducer for reflection from the actuators. The reflected energy is detected, and the actuated key is identified based upon the transit time of acoustic energy from the transducer to the detector via reflection off of the reflector member associated with the actuated key.

Abstract: A process for manufacturing optocouplers having an emitter element properly oriented with respect to a receiver element. An emitter element is fastened to an emitter carrier. A receiver element is fastened to a receiver carrier. The emitter and receiver carriers are positioned adjacent one another to bring the emitter and receiver elements into operative relation. The combined operation of the emitter and receiver elements is electrically monitored while the position of the carriers with respect to one another is adjusted. On the basis of the electrical monitoring, a determination is made as to when a proper orientation between the emitter and receiver elements has been achieved. The emitter and receiver carriers may then be permanently bonded together for subsequent final packaging. The process described is particularly well suited to automated manufacturing.

Abstract: Polycrystalline silicon is obtained by providing a silicon wafer having disposed over at least one face thereof a base coating of oxide, nitride or oxynitride composition, forming a substantially pinhole-free and scratch-free layer of carbon on said base coating over at least the face, forming on the face of the carbon layer a layer of polycrystalline silicon, and removing the silicon layer from the protective coating. Any of the carbon layer adhering to the silicon layer is easily removable to provide the silicon layer separate from the substrate. The wafer/coating unit is reusable in the procedure. The wafer/coating/carbon layer unit comprises a workpiece useful in the practice of the invention.