376 



'Popular Science Monthly 



tape with various combinations of holes. 

 In the illustration the fresh tape may be 

 seen unrolling from the reel back of the 

 rack carrying the message about to be 

 sent. After perforation at the left end 

 of the keyboard machine, the tape passes 

 under the pivoted arm of an automatic 

 stop and then into a transmitter unit (at 

 the extreme left of the photograph). 

 The operator ordinarily punches tape at 



These eight operators work at one end of a single trunk 

 line. Four are sending and four receiving, and they are 

 kept busy every minute. The same number work on 

 the other end of the wire, and it is possible to send more 

 than six thousand messages over one wire in a single 

 working day 



about the speed of transmission, so that 

 a little slack tape hangs under the con- 

 trol arm of the stopping device. Should 

 he fall behind, however, as soon as the 

 transmitter uses up the loose tape and 

 so begins to stretch it tightly between 

 the two machines, the control arm is 

 lifted. This operation automatically 

 stops both the local transmitter and the 

 receiver at the distant end until more 

 letters are perforated. Then the tape 



slackens, the control arm drops and 

 transmission begins again. Thus the 

 printed message appears complete and 

 without blanks, even though the trans- 

 mitting operator is forced to stop in the 

 midst of perforating. 



The printing receiver is shown in an- 

 other photograph. Inside the case a 

 message is being typewritten as the per- 

 forated tape corresponding to it passes, 

 letter by letter, through the 

 transmitter. Each group of 

 five impulses (one for each 

 row of punched holes in 

 the sending tape) prints a 

 single letter, makes a space 

 between words or starts a 

 new line on the printed 

 page by returning the pa- 

 per-carriage to the right 

 and turning up the paper. 

 At the end of each mes- 

 sage a short time is al- 

 lowed for the receiving op- 

 erator to take cut the 

 printed telegram and in- 

 sert a fresh blank; while 

 the new message is being 

 typed he checks over that 

 which has just been re- 

 ceived and, if it seems cor- 

 rect, turns it over to the 

 delivery department. ■ 



The printing, ready for 

 delivery, of keyboard-per- 

 forated messages, could be 

 accomplished by any of the 

 older successful page-print- 

 ing telegraph systems. In 

 fact, the same line could be 

 duplexed and messages 

 sent at about fifty words 

 per minute in both direc- 

 tions, so keeping four op- 

 erators at work on a single 

 wire. But the new printing 

 telegraph is capable of handling the tele- 

 graphic output of eight transmitters and 

 thus keeping sixteen operators busy over 

 one line. This simultaneous transmission 

 of messages is made possible by the use 

 of a pair of special distributors, one at 

 each end of the line, which successively 

 switch in and out each of four sets of in- 

 struments. The line is duplexed and 

 therefore permits messages to travel in 

 both directions at the same time ; for each 



