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BELL SYSTEM TECILXICAL JOURNAL 



sumed that the direct-current telegraph circuit is worked at as high 

 a speed as the frequency range assigned to it will permit. 



A number of different wave forms which might be employed to 

 make up the telegraph signal elements will next be examined, con- 

 sideration being given first to the waves which will be received at the 

 distant end when the different wave forms are impressed at the trans- 

 mitting end and second to the interference which will be produced 

 in the higher range of frequencies which has been assigned to other 

 uses. 



Three forms of voltage waves which will be considered are shown 

 in Fig. 1. .1 in that figure shows the simplest form of voltage wave, 





L.=TR/8 



C, = 2/JT2PTR 



C2 = T/4R 



f = Carrier Frequency 



Fig. 1 



A — Rectangular Voltage Wave 

 B — Half Cycle of Sinusoidal Voltage Wave 



C — Rectangular Voltage Wa\c Modified by Being Passed through Network 

 Shown at D or E. 



namely, the raclangular ff)rm which is protlucctl \i\ ap|)King a battery 

 for a given intcr\al of time and tiien substituting a short circuit 

 for it. C in the figure is the wave produced by transmitting the 

 rectangular voltage wave A through an electrical network which is 

 the one indicated by the letter D in the figure. (Other forms of 

 networks might also be selected which would produce similar results.) 

 B in the figure is a wave which has the shape of a half CNcle of a sine 

 wave. In what follows this wa\e will be referred to as ihe "half- 

 cycle sine wave." 



In considering the waves which will be received when the abo\e 

 waves are applied at the transmitting end, use will lie made of the 

 following general principles, which have been stated b\' Malcolm,' 

 for the case of a submarine cable circuit and discussed for the general 

 case in Appendix A. 



' H. W. Malcolm. "Theory of the Submarine Telegraph and Tiitphone Cable." 

 The Klectriiinn Printing & Piiblisliing Co., London, .\larih l')17. 



