Title: Apparatus utilizing analog-to-digital conversion in the photoelectric reading of documents

Abstract: An examination answer sheet, on which the examinee has darkened certain discrete areas with a graphite or lead pencil to denote his selected answers to multiple choice questions, is moved relative to a plurality of photoelectric cells, these cells providing analog voltages having magnitudes in accordance with the opacity of the marks or data on the sheet. During time intervals derived photoelectrically from a sequence of marks constituting a timing track, the highest voltages provided by the data cells are individually stored, later digitized, and the digital information forwarded to a computer for comparative processing with answer information contained in the computer's memory.

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Inventors: Firehammer, John D. (Burnsville, MN, US)
Gruebele, Dale W. (Bloomington, MN, US)

Application Number: 268445
Filing Date: 1972-07-03
Publication_date: 1976-09-28
Assignee: National Computer Systems, Inc. (MN)
Primary Class(es): 434/358 235/440, 235/454
Other Classes:
US Patent Ref:

2937369	May, 1960	Newbold et al.	340/347.
2978535	Apr, 1961	Brown	179/15.
3059228	Oct, 1962	Beck et al.	340/347.
3201569	Aug, 1965	Conron	235/61.
3363113	Jan, 1968	Bedingfield	328/151.
3487560	Jan, 1970	Hassfurther et al.	35/48.
3495235	Feb, 1970	Ottesen	340/347.
3524048	Aug, 1970	McMillin	235/61.
3536895	Oct, 1970	Dedden et al.	235/61.
3603975	Sep, 1971	Gordon	340/347.
3629496	Dec, 1971	McConnell	178/DIG.
3692982	Sep, 1972	McMillin	235/61.
3718910	Feb, 1973	Scray et al.	328/151.
3737628	Jun, 1973	Azure	35/48.

Other Refs:
Primary Examiner: Sloyan, Thomas J.
Assistant Examiner:
Attorney: Peterson; Stuart R.