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Claim 1

AN ANALOG-TO-DIGITAL CONVERTER, INCLUDING: A ROTATABLE OPTICAL DISC HAVING A PLURALITY OF CONCENTRIC CODE RINGS REPRESENTING THE DIGITS OF A NUMBER; A STATIONARY LIGHT SOURCE FOR PROVIDING LIGHT ALONG A THIN RADIAL AREA OF SAID DISC ACROSS EACH OF SAID RINGS, EACH OF SAID CODE RINGS HAVING A NUMBER OF ALTERNATE SECTIONS TRANSPARENT AND OPAQUE RESPECTIVELY TO THE LIGHT FROM SAID SOURCE SO THAT AS SAID DISC ROTATES DIFFERENT COMBINATIONS OF TRANSPARENT AND OPAQUE SECTIONS ARE LINED UP IN THE THIN RADIAL AREA OF LIGHT; A STATIONARY PHOTEMISSIVE VACUUM TUBE POSITIONED ADJACENT SAID DISC ALONG THE PATH OF THE LIGHT FROM SAID SOURCE SO THAT THE LIGHT ALONG SAID THIN RADIAL AREA WHICH PASSES THROUGH A TRANSPARENT SECTION OF ANY ONE OF THE CODE RINGS ENTERS SAID TUBE, SAID TUBE INCLUDING A TRANSLUCENT PHOTOEMISSIVE CATHODE HAVING AN ELECTRON EMISSIVE SURFACE AT LEAST AS LARGE CIRCUMFERENTIALLY AS SAID THEN RADIAL AREA ILLUMINATED BY THE LIGHT FROM SAID SOURCE; AND AN ELECTRON RECEPTOR FOR EACH OF SAID CODE RINGS POSITIONED ADJACENT SAID ELECTRON EMISSIVE SURFACE FOR RECEIVING THE ELECTRONS EMITTED FROM THE PORTION OF SAID SURFACE ADJACENT THERETO, SAID ELECTRON RECEPTORS BEING ARRANGED IN A ROW PARALLEL TO SAID THIN RADIAL AREA SO THAT SAID RECEPTORS ARE SELECTIVELY ENERGIZED IN ACCORDANCE WITH THE CODING DETERMINED BY THE TRANSPARENT SECTIONS OF SAID RINGS ALONG SAID THIN RADIAL AREA ILLUMINATED BY THE LIGHT FROM SAID SOURCE.