A plurality of optical transmission tracts direct radiant energy from an appropriate light source to each of a plurality of photo-transistors or other light sensitive elements. The photo-transistors are adapted to generate an output signal whenever the radiant energy impinging thereon exceeds a threshold value which distinguishes environmental radiation from the radiant energy generated by the light source. A plurality of code bars, each representative of a different character code, are provided. Each code bar includes a hinged rail pivotally coupled to the housing and a plurality of radiant energy interrupting code projections depending therefrom. The number and location of the plurality of radiant energy interrupting code projections depending from each hinged rail is determined by the character code associated with the code bar of which they form a part. Each code bar is movable from a first position wherein its radiant energy interrupting code projections do not block the transmission of radiant energy from the light source to the photo-transistors, to a second position wherein the radiant energy interrupting code projections do block the transmission of radiant energy from the light source to selected photo-transistors. The movement of each code bar is controlled by a different, independently operable, push-button.

The invention relates to photo-optical detection by coded aperture in which photo-optical keyboard apparatus includes a pattern arrangement of keys in rows and columns wherein each row is provided with a light source or generator optically couplable to a light receiver or receptor and including individual key stems each of which is provided with a light transfer attenuating, limiting or constricting element each element being arranged to pass or restrict a percentage of the light from source to receptor, key to key, by column to row effective to indicate the precise key position or location as a result of the actuation or depression of any key in the pattern arrangement. By electrically multiplexing the light signals a minimum circuit complex is required.

This invention relates to a novel shift lock actuation mechanism useful, for example, in keyboard apparatus wherein a key stem supporting a key is shaped to mate with apertures in the keyboard supporting arrangements or as individual switches and as such contains oppositely disposed, inwardly deformable, flanged members for captivating the key stem within the key apertures and further includes a shift lock cam operably associated with a single turn C-shaped torsion spring member, one end of the C-shaped spring engaging key stem while the opposite end of the C-shaped spring is captivated by the cam, effective upon movement of the key stem to move the cam into one or the other of two positions effective to lock the key stem in a desired position so as to block or unblock light from light emitter-receptor apparatus indicating the position of the key.

A light actuated switch apparatus is described in which no movable switch contacts are employed. The switch uses a light source and shutter to activate an array of light sensitive devices to generate a binary code that provides the switching function. One embodiment of the switch apparatus is employed inside a control knob providing a binary code generated by shutter action of a light source on an array of phototransistors. Another embodiment employes the above control knob including switch apparatus as well as a second knob and printed board to form a dual switch apparatus. As no switch contacts are employed there is considerable reduction in electrical components. Additionally, this also greatly reduces the space required for mounting the switch, is readily serviceable or replaceable as no parts are located within an instrument, and is less expensive as no contacts eliminate any wear and potential problems associated with movable through stationary contacts.