Popular Science Monthly 



609 



student plan of learning will of course 

 develop both the speed and reliability 

 needed, a little at a time, but for the best 

 results there should be some way to check 

 and eliminate possible errors in sending 

 which may pass by both students quite 

 unobserved. The best way to take care of. 

 this difficulty is by 



the cooperation of a ^1*1*1 



skilled "operator, as 

 explained above. If 

 no such help can be secured, 

 the next best plan is to use 

 an automatic sender of 

 some sort. Such an auto- 

 transmitter, driven by clock- 

 work or by a small electric 

 motor, can be used in self- 

 instruction or by a group of 

 students. Several types are 

 available, but the two most 

 employed use metal disks or 

 paper tapes already pre- 

 pared and carrying various 

 combinations of words and 

 letters in common usage. 



The Disk Sender 



The operation of the metal disk type is 

 indicated in Fig. 9, where the disk itself is 

 shown rotating in the direction of the arrow 

 and having notches cut around its circum- 

 ference to correspond with dots, dashes and 

 spaces. As the disk re- 

 volves, the point on the 

 spring arm P moves back 

 and forth along the irregu- 

 lar teeth, and the contacts 

 A and B are brought to- 

 gether and separated to 

 form dots and dashes. 

 When the contacts are 

 pressed together the bat- 

 tery circuit from the dry 

 cells D through the buzzer 

 Z is closed by way of the 

 pivot /, spring 5 and bind- 

 ing post C, and the buzzer 

 sounds. A short tooth on 

 the disk produces a dot 

 signal, and a long tooth a 

 dash. Thus the notches 

 shown in Fig. 9 would produce dot-dash, 

 space, dash-dot-dot-dot, or the letters "A" 

 and "B" separated by a space. 



The metal signal-disks are made up in 

 great variety, and are interchangeable so as 

 to form complete message's. For beginning 

 of practice there are disks giving the letters 



▼. " r Ba 



Diagram of connections for an 

 automatic sender in a line 



1 



2 



3 



4 



5 



6 



7 



8 



9 





 PERIOD 

 COMMA 

 INTERROGATION 

 PARENTHESIS 

 QUOTATION 

 DOUBLE DASH 



FIG 12 

 The numerals and the most used 

 punctuation marks in telegraphy 



of the alphabet singly and in regular order, 

 and also in mixed order. This last named 

 arrangement is especially desirable for 

 practice, since it is almost impossible to 

 anticipate the letters about to be sent, and 

 the student is forced to listen closely and 

 think quickly in writing the letters as they 

 occur in what 

 line wire _ amounts to a long 



cipher word. Several 

 forms of the disk 

 sender are made, under 

 the trade name of "Omni- 

 graph," in which the disks 

 are rotated either by hand 

 or by clockwork. The 

 automatically driven type 

 , is by far the best for seri- 

 ) ous work, since its speed 

 may easily be adjusted to 

 almost any rate which oc- 

 curs in telegraphy, and, 

 once started, the instru- 

 ment may be put com- 

 pletely out of mind and 

 full attention given to 

 writing out the letters and words pro- 

 duced by the buzzer. 



The Paper Tape Transmitter 



Another sort of automatic sender is 

 shown in Fig. 10, in which a cut paper tape 

 passes between a spring contact and a 

 metal roller. The sketch 

 shows how the "slip" is 

 threaded over a guide rol- 

 ler G and between the two 

 driving rollers E and F 

 which turn in the direc- 

 tions indicated by the ar- 

 rows. The spring contact 

 H bears down on the 

 paper, and, when a hole 

 in the tape comes under it, 

 makes contact with the 

 metal roller F. This closes 

 the battery circuit from 

 the cells B through the 

 buzzer Z, and the buzzer 

 reproduces the dots and 

 dashes cut in the paper 

 strip. On the left is 

 shown the letter "R" (dot-dash-dot) and 

 on the right the letters "A" (dot-dash) and 

 "I" (dot-dot). An automatic transmitter 

 of this general sort, in which the tapes are 

 cut to give various word and letter combina- 

 tions, is sold under the name of the "Audi- 

 ble Alphabet." The instrument is driven 



