610 



by turning a small crank by hand, but it is 

 not difficult to gear a small electric motor to 

 operate it and thus to afford true automatic 

 operation. 



Any sort of automatic transmitter can be 

 made very helpful in learning the code. 

 The apparatus is not very expensive, and if 

 five or six students combine to purchase one 

 together the cost to each individual becomes 

 extremely low when compared with the 

 benefits secured from having a tireless 

 sender of perfect Continental Morse signals 

 which will give practice as long as it is 

 wanted. Fig. 1 1 shows how to connect the 

 automatic sender at one of the stations of a 

 multiple-station buzzer-telegraph line. The 

 balance of the stations are wired in ac- 

 cordance with Fig. 8. The automatic 

 sending station of Fig. 1 1 may be chosen to 

 be somewhere near the middle of the tele- 

 graph line, so as to give about equal 

 strength signals at both ends; the line wire 

 extending to the other instruments is in- 

 dicated by the broken line at the top of the 

 figure. The telephones T are shown shunted 

 by the signal-intensity regulating resistance 

 R, and connected between the line wire and 

 the vibrator post contact of the buzzer Z. 

 The two outer terminals of the buzzer are 

 connected in series with the battery B, a 

 single-pole double-throw switch S, and 

 either the hand-sending key K or the auto- 

 matic transmitter A. The armature post 

 of the buzzer is connected with ground at E. 

 When the switch 5 is in position / the hand 

 key is connected, and signals may be trans- 

 mitted in the usual way. When the switch 

 arm is in position 2, the key is cut out and 

 the automatic transmitter placed in circuit. 

 The signals which it sends out are trans- 

 mitted both up and down the line, and may 

 be copied simultaneously by all the students 

 at their respective home stations. 



Morse Practice on the Buzzer Line 



By arranging a definite time schedule for 

 running the automatic sender, it is possible 

 to work out a scheme of daily Morse 

 practice at gradually increased speeds, 

 until finally all the learners are able to 

 write down messages at a speed of from 

 twenty to twenty-five five-letter words per 

 minute. To make the practice comprehen- 

 sive it is necessary to arrange for periods of 

 sending practice for each of the stations, in 

 which one student sends messages or press 

 notes from the newspapers and all the 

 others copy his signals. The messages as 

 copied by each one should be carefully 



Popular Science Monthly 



compared with the original as it was sent 

 out; errors in receiving can be located by 

 reason of their appearing on only one of the 

 copies, while errors in transmitting should 

 show up in all of the copies. Practice of 

 this sort, varied by the exchange of mes- 

 sages between various pairs of stations on 

 the line, will give the most valuable training 

 which it is possible to secure outside of 

 actual radio telegraphy. 



In the first article the Morse symbols 

 corresponding to the twenty-six letters of 

 the English alphabet were given. Fig. 12 

 shows the numerals and the more usual 

 punctuation marks. These should all be 

 memorized and used in the message 

 practice. Entire familiarity with the code 

 as thus completed will come with the daily 

 sending of dispatches, and a few months of 

 this work should make any apt student a 

 fairly, skilful telegrapher. 



In the next article the formal methods of 

 sending messages with full preambles, ac- 

 cording to the International Radiotelegraph 

 Convention, will be explained and illus- 

 trated, and the problems of reading 

 messages and signals through interference 

 from other radio stations and from "static" 

 or atmospheric electrical disturbances will 

 be discussed. 



(To be continued) 



The Underwriter's Knot for 

 Flexible Cords 



FLEXIBLE cords used to suspend a 

 lamp should be arranged so that there 

 is no stress 

 or strain 

 coming on 

 the binding 

 posts or con- 

 n e c t i n g 

 screws. To 

 provide a 

 suitable 

 holding 

 means, 

 knots should 

 be tied in the cord to make them take all 

 the weight of the socket and fixture from 

 the ends of the wire. The successive steps 

 in tying the knot are shown in the illus- 

 tration. 



While these knots may appear to be of 

 no use they are absolutely necessary, not 

 only to relieve the strain, but to fulfill 

 the requirements of the underwriters' code 

 for safety in insurance. 



A knot tied in line in such a way 

 as to take the strain from a fixture 



