Another type of machine is built on the same principle as the book-keeping machine of cash-register design. Twenty-seven keys, each representing a classification, accumulate individual totals and as many as three grand totals can be obtained and the number of items in each classification counted. A continuous permanent record of all operations is made within the machine on a roll of paper called a visible audit sheet, and notations may be hand-written opposite any printed item. This record may be used as a posting medium, a proof sheet or a permanent record. A ticket may be issued on any operation, showing the date, serial number, identifying numbers, symbols for the totals used and the amount. It may be used as a voucher, pay ticket, receipt, requisition or posting medium or for filing purposes. The same information may be printed on any form inserted in the printing table.
In offices there is much need for devices that will quickly produce multiple copies of typewriting or handwriting, for the time and labour thus saved is an impor tant economy. Sometimes only a few copies are needed, some times many. For a limited number of copies, say up to five or six, the carbon method of duplication is perhaps the cheapest in most cases; but where from 5 to i oo copies are required, the hektograph process is preferable.
For a still larger number of copies, the stencil methods and type methods are available. With the former, the stencil was originally made on a sheet of wax-covered paper, which was written upon either with a stylus or with a typewriter from which the ribbon was removed—a system that had many defects. The modern method utilizes a specially prepared sheet of tough, flexible tissue, which can be filed away after using and used many times. One manufacturer provides a glass-topped, electrically illuminated table for making stencils by hand with a stylus. Typewriting, handwriting and drawing may all be com bined on one stencil sheet. The duplicator consists of a hollow revolving cylinder, partially covered by an ink pad, over which the stencil is fastened. Each revolution brings the stencil sheet in contact with the paper, and the ink, passing through the character or design, makes the impression. From 1,5oo to 5,000 copies can be made in an hour, depending on whether the model is hand- or motor-operated and whether it is automatically fed.
The hektograph is many years old, and its operation is based on the principle of absorption. The original writing is done on a sheet of hard bond paper with a water soluble ink or with a typewriter ribbon impregnated with such ink. This sheet is then placed in contact with a moist surface of gelatin or clay composition, and the writing is absorbed from the paper and appears in reversed form on the gelatin or clay surface.
Then, by placing a sheet of blank dry paper on this moist surface, the impression is transferred to the paper. The gelatin was originally used in flat tin pans, and in this form the hektograph was of little use in the office, as registration was difficult. The clay form of hektograph was, and is, extensively used for the reproduction of drawings by architects and draftsmen, because it is a simple matter to prepare this composition for large sizes of work. The modern hektograph uses the old principle, but the gelatin is coated on a long band, a small portion of which is exposed at a time. This band runs over a flat iron surface. Registration is accomplished by a special feeding device. The unique feature of the hektograph duplicator is its use in routines of order or billing systems, in which from i o to 15 copies of the same writing (or any portion of it) may be transferred to sheets of various sizes and shapes. Such copies are much clearer than carbons, and the paper does not have to be thin. The hektograph can also be used for bulletins of which i oo or less copies are desired.
There are several devices which dupli cate from type, the principal feature of most being a simple method of setting the type, which does not require a trained type setter, the printing also being simplified by means of a revolving drum. The style of type most used is the imitation typewriter face, and the chief use is for the reproduction, through a ribbon, of facsimile typewritten letters, there being also a special device which may be used for the reproduction of the signature. A printing-ink attachment makes possible the use of printer's type and of electrotypes or stereotypes curved to fit the drum. Some models are hand-fed and operated; those which are automatically fed and motor driven attain a speed of 2,400 to 4,800 pieces an hour. Another machine produces letters from typewriter type cast on a linotype machine, at the same time filling in the name, address and salutation from slugs—one for each name on the mailing list—which change automatically as each letter is printed through a ribbon, the slugs being filed for future use. The speed is I,000 letters and envelopes an hour, the latter being addressed from the same slugs. Certain machines which print from type writer type are really small presses adapted to the printing needs of the layman, and print from printer's type, electrotypes, lino type, monotype, flat zincs and half-tones.