Cl-RI.IIX FACTORS AFFECTING TEUIGRAPH SPEED 345 



tlu> spaiiiiK botwiH'n tlu- dots. The ri-sult of this is to iiureasi- the 

 nuniluT of Kourior compononts in a given frtHjucncy ranjje aiul to 

 decrease the niagnitiule of each. If this process of increasiiijj; ilie 

 space between the dots is continued indefinitely, we approach the 

 coniiition of an isoIate<l dot. Moreover, as we approach this condi- 

 tion, the nunil)er of conijionents in a given frequency range increases 

 indefinitely and the magnitiide of each decreases indefinitely. This 

 limiting result is known as the Fourier integral for the \va\e in question. 



.\ri'l.\|i|\ 1) 



A table has been given in the paper in which the relative efficiency 

 of various ccnles in transmitting intelligence is listed. The deriva- 

 tion of that table will now lie given. 



The comparison will include the following codes based on two 

 current \alues: American Morse, Continental Morse, and the so- 

 calleti "ideal" two-currcnt-value code. It will also inckKle the fol- 

 lowing codes based on three current \alucs: CoiUim-iUa! Morse 

 and an "ideal" three-current-value code. 



The assumption is made that the text is made up of fi\e-letter- 

 words, no allowance being made for punctuation. The following 

 table gives the length of the spaces assumed in terms of signal elements. 



Ordinary Special 



Spaces Spaces in Spaces Spaces 



Within "Spaced" Between Between 



Letters Letters Letters Words 



American Morse ftwo current values') 1 2 3 4 



Continental .Morse (two current values) . . 1 — 2 3 



Continental Morse (three current values). . — — 1 2 



It is assumed that the dashes in the two-curreiU-\ulue codes are of 

 three signal elements duration, e.xcept for the letter / in American 

 Morse which is assumed to occupy five signal elements. It may be 

 that in practice, the dashes are somewhat shorter than has been 

 assume<l but the resulting error is not great. In connection with the 

 relative spacings between letters and words assumed for the Conti- 

 nental and American Morse codes, it is also questionable whether 

 they accord strictly with practise. It may be that these spacings are 

 on the average more nearly equal than the table indicates. However, 

 this assumption affects only the relative speeds obtainable with the 

 American Morse and the Continental Morse and does not materially 

 affect the comparison between codes based on two current values on 

 the one hand and ctxles based on three current values on the other. 



The term "ideal" has been applied to two codes which will next 

 be explained. These ccnles are constructed on the same principles 



