506 



BELL SYSTEM TECILMCAL JOURNAL 



In all of the systems in which bandwidth may be exchanged for tolerance 

 to interference we restrict, in our comparison tables, the minimum band- 

 widths to those which provide at least the 44 db tolerance demanded in the 

 two-frequency plan. 



RECTANGULAR ENVELOPE THROUGH GAUSSIAN FILTER 

 ORIGINAL DURATION TIME X R-F BANDWIDTH BETWEEN ONE NEPER POINTS = 2 



-1.4T -1.2T -T -0.8T -0.6T -0.4T -0.2T 0.2T 0.4T 0.6T 0.8T T 1.2T 1.4T 



TIME IN TERMS OF T 



0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 J_ 1.1 



TTTTTTTTTT 

 FREQUENCY IN TERMS OF T (fROM MIDBAND) 



1.3 



T 



1.4 



T 



Fig. 6 — Basic pulse shape (approximately sinusoidal) and its spectrum. 



II. B.vxD Width C'h.\k.\cteristics 



The type of pulse assumed in the various pulse transmission systems is 

 shown on Fig. 6. As pulse 4 of Fig. 26, it is further discussed in Section VII. 

 The si)ectral density or distribution of energy vs. frequency associated with 

 such a pulse is also shown. It is evident from this curve that omission of 

 frequencies beyond a baseband width \'T can result in distortion or tails of 



