History of the Typewriter

—307— tape, somewhat after the fashion of a mechanical piano. Hie speed of the printer is now very high, not less than Z5O words (900 letters) a minute, but practical considerations oi durability and maintenance of the typewriter, limit tlæ speed at present to about zoo or 120 words a minute, ine limit of speed in transmission of the signals over the line is in the receiving perforator which reproduces the tape at the distant station. With the improved machinery now in use, it has recently been found possible to punch -he received tape faultlessly at the rate of 184 words (1,104 letters) per minute. At this speed no less than ninety-two holes per second have to be punched in the paper tape successively by a single punch. A similar group of machines in the reverse order are required for transmitting messages in the opposite direction on the same wire at the same time. It was a model of the printer, at that time in a very crude form, that Mr. Murray took to New York in 1890. In New \ ork the electrical portion of the system for per- forating the tape, transmitting the signals and perforating L ic received tape, was evolved. At that time the printer aPPeJred be a sort of combination of sewing machine and barrel organ. An operator had to work the printer a lianc^e> and the machine was variously known as Murrays coffee mill,” and “the Australian sausage machine, but more frequently as “ the Baby.” In London the printer was very greatly improved. An electric motor to drive it was provided, and all the actions were made automatic the machine stopping at the end of each line, running the typewriter carriage back, turning up a new line, and starting again, and finally stopping at the end of each message, all under the control of the perforations m taPe- A very necessary improvement was a method of invisible correction of errors in the trans- mitting tape. \\ ith the system in its now perfected form, if an operator on one of the keyboard perforators at the sending station strikes a wrong key or perforates a wrong word, all he or she has to do is to press a back-spacing ever and a rub-out ” key once for each wrong letter. Ihis action punches the erroneous portion of the tape nil of holes so as to obliterate the wrong letter or letters. This obliteration is reproduced in the receiving tape at tlie distant station, but the printer is so arranged that it stops work for the moment during which the obliterated portion of the tape is passing through it. The result is at no trace of the error, not even a blank space, appears in the printed message.