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BELL SYSTEM TECHNICAL JOURNAL 



the component waves of each delayed portion. Thus the first opera- 

 tion spreads the wave out on a time scale, the part of the original wave 

 corresponding to the frequency range having the minimum slope ar- 

 riving first and followed successively by portions corresponding to the 

 remaining frequency ranges. The relative delay for a range A/ is 

 given by the difference between the slope of the phase characteristic 



-2Tr 



Fig. 2 — A curved phase characteristic. 



in the range A/ and the minimum slope. This difference or the expres- 

 sion [{dB/doo)f — (dB/do))min\ is spoken of as the delay distortion. The 

 delay distortion characteristic is simply a graph of the above expression 

 plotted against frequency. The second operation distorts the wave 

 forms of the delayed portions corresponding to the frequency ranges 

 A/, thus making it impossible to speak of the delay of the final or re- 

 ceived portions or of the received wave as a whole. 



This may be described in other terms by saying that a network hav- 

 ing a characteristic of the type shown in Fig. 2 may be thought of as if 



