Abstract: Marks on test answer sheets and the like are detected by scanning with fiber optic line-to-circle converter using a single photocell. Four to five rows of optical fibers each about 2 to about 3 mils thick make up the fiber optic line, and the fiber optic "circle" is an arc no greater than about 95% of a circle. Scanning can be compensated for flaws in the optics and for poor response when photocell begins scanning the arc. Sheets are fed in spaced sequence, the feed is deactuated momentarily and then reactuated in synchronism with the scanning. Electrically operated clutch-brake assembly with spring-carried clutch plate makes good synchronizer particularly when clutch is opened for not over 0.1 second and is closed by a current pulse at a voltage substantially greater than used for holding it closed.

Abstract: Marks on test answer sheets and the like are detected by scanning with fiber optic line-to-circle converter using a single photocell. Four to five rows of optical fibers each about 2 to about 3 mils thick make up the fiber optic line, and the fiber optic "circle" is an arc no greater than about 95% of a circle. Scanning can be compensated for flaws in the optics and for poor response when photocell begins scanning the arc. Sheets are fed in spaced sequence. Electrically operated clutch-brake with spring-carried clutch synchronizes feed with scanning, particularly when clutch is opened for not over 0.1 second and is closed by a current pulse at a voltage substantially greater than used for holding it closed. Electronic logic can disable the equipment if markings on sheets show that improper control sheets are used. Scoring can be checked by verifying count of control sheet markings each time a test sheet is scored.