Abstract: A frame attachable to the numbering shaft of a conventional printing press supports and guides belts bearing print elements side-by-side across a printing head such that the belt paths define parallel columns and drive and indexing means position the belts such that print elements fall in selected rows to define at least one predetermined code pattern which prints a machine readable code.

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.