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The term unit record equipment also refers to peripheral equipment attached to computers that reads or writes unit records, e.g., card readers, card punches, printers, MICR readers. IBM was the largest supplier of unit record equipment and this article largely reflects IBM practice and terminology.
In its basic form, a tabulating machine would read one card at a time, print portions (fields) of the card on fan-fold paper, possibly rearranged, and add one or more numbers punched on the card to one or more counters, called accumulators. On early models, the accumulator register dials would be read manually after a card run to get totals.
During 1907, the company was renamed the "British Tabulating Machine Company Limited". In 1920, the company moved from London to Letchworth, Hertfordshire; it was also at this point that it started manufacturing its own machines, rather than simply reselling Hollerith equipment. Annual revenues were £6K in 1915, £122K in 1925, and £170K in 1937.
The paper chart is driven past the pen at a steady rate by a clockwork or electrical drive mechanism. One common method is to use a miniature synchronous motor which turns at a constant speed related to the power frequency; a gear-train is used to propel the paper. Industrial strip-chart recorders may have two-speed gear trains that allow a ...
Unit record" data processing equipment uses punchcards to carry information on a one-item-per-card basis. [15] [16] Unit record machines came to be as ubiquitous in industry and government in the first two-thirds of the twentieth century as computers became in the last third. They allowed large volume, sophisticated data-processing tasks to be ...
In 1907, Powers was hired by the US Census Bureau as a mechanical expert to modify unit record equipment invented two decades earlier by Herman Hollerith. Hollerith's equipment was successfully used for the 1890 and 1900 US Censuses, but when Hollerith refused to lower the rental fees for the Census Bureau, the Bureau's director S.N.D. North ...
Friden manufactured equipment which could connect their calculators to Flexowriters, printing output and performing unit record tasks such as form letters for bills, and eventually manufactured their own computers to further enhance these capabilities. These variants were sold as the Friden Computyper. Computypers were electromechanical; they ...
Powers-Samas machines detected the holes in punched cards mechanically, unlike IBM equipment where holes in punched cards are detected by electrical circuits. Pins that could drop through round holes in punched cards were connected to linkages and their displacement when a hole was present actuated other parts of the machine to produce the desired results.