Page:Popular Science Monthly Volume 91.djvu/772

 Telegraphing by Typewriter

How one telegraph company doubled its facilities without adding a single wire

��TO provide adequately for the handling of its enormously increased business, the Western Union Telegraph Com- pany was recent- ly confronted with the problem of doubling its serv- ice facilities. To double the number of telegraph lines, and therefore, to increase the num- ber of employees, was too costly for serious considera- tion. Automatic telegraph oper- ators were in- stalled. Their speed is so great that more than twice the number of telegrams formerly handled can now be sent over the same lines.

This is how it was made possible. Typists take the place of key operators. As they operate special typewriters, they perforate a narrow strip of paper with a number of holes, the arrangement of which varies with each letter of the alphabet. A strip of paper is to the new system of telegraphy what the music roll is to the player-piano. As a given perforation in the music roll determines the note to be played, so a tape perfora- tion determines the letter to be printed at the receiving sta- tion. A tape is type- written and drawn through the electric transmitters© quick- ly that one thou- sand, six hundred and fifty words can be sent in the time required by one typ- ist to send a thou- sand words with the regular key.

Thus the company has increased the amount of business it handles by sixty-

���The device by means of which four messages come and four go over the same wire at the same time

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��Typists operate special machines which make records of the messages in perfor- ations on paper like player-piano records

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��five percent, without the addition of a single new line! It did not stop at that, however. Key operators can work "quadruplex" — that is, four of them -can send their messages over a single wire, two in one direc- tion and two in the other direction at the same time. The typewriters were made to do the same. We thus come to the second improvement, a device which al- lows four messages to be transmitted from the sending to the receiving station and four in the opposite direction from the receiving to the sending station at the same time and over the same wire! Two brushes, one at each station, rotate over four segments at the same speed and come in contact with corresponding seg- ments at all times. At one station, the four segments connect with the four tape transmitters; at the other, they connect with the four printing machines. While one transmitter is sending a letter to its corresponding printer, the brushes will be moving toward the next segment. The printer levers will select the letter and will print it on the regular telegram blank while the brushes are rotating over the three re- maining segments. The first printing set is then ready for the next letter. This happens with every segment, so that with each complete revolution of the brushes, one letter will have been sent and received by four operators.

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