The importance of copying processes ONE of the most frequently occurring requirements in all modern human activity, be it commerce, government, research, or any other sphere, is the need to obtain a true copy of a document. The efficiency of the method used for copying documents has a definite influence on the overall efficiency of the undertaking concerned. Executives are therefore always on the look‐out for improved methods for copying documents. By ‘document’ is meant any visual record of information. The information may be expressed by various media, such as language, numerical data, codes, graphs, diagrams, sketches, or photographs, which may be borne on various vehicles, such as letters, memoranda, reports, drawings, tracings, blue‐prints, pamphlets, patent specifications, periodicals, books, photographic film, index cards, and punched cards.