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BELL SYSTEM TECHNICAL JOURNAL 



out in F"ig. 3. Fig. 3a shows the words "United States" written in 

 the code advocated by Squier. Fig. 3fr shows a constant sine wave 

 whose amplitude is equal to the amplitude of a dot in Fig. 3a. Fig. 3c 

 shows the result obtained by subtracting the wave of Fig. 'ib from 

 the wa\e of Fig. 3(i. On coinixuing this last wave with the wa\e 



_i\ 





Fig. 3 



a — Unbroken reversals code (space = 1 unit, dot = 2 units, dash = 3 units) 

 b — Constant sine wave, 2 units 

 c — Wave resulting when substracting b from a 

 d — Sine Wave code: note similarity between c and d 

 e — Rectangular wave, unmodified 



/ — Rectangular wave, modified by grounding apex one fourtli of the marking 

 time in addition to the spacing time 



shown in Fig. Zd, it will be seen that the two waves are electrically 

 equivalent. They differ only in having the signal elements permuted. 



It is thus evident that the wave shown in Fig. 3a is made up of two 

 components; one being the inert component shown in Fig. 36 which 

 transmits no intelligence, and the other the intelligence carr\ing 

 coniiX)iient illustrated in Fig. '.\c. 



The fact that the component shown in Fig. Ab docs not carry in- 

 telligence from the sending station to the receiving station is made 

 clear when we consider that its value at any moment is predictable 

 and that the component can in fact be produced localK'. 



The net effect of this component is to reduce the voltage a\ailable 

 for intelligence transmission to one-third of the total voltage. For 

 example, if it is permissible to apply 60 volts to a particular cable, 

 40 volts out of these would be used up in transmitting the inert alter- 

 nating-current wave and only the remaining 20 volts would be useful 

 for the transmission of intelligence. 



