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BELL SYSTEM TECHNICAL JOURNAL 



total applied voltages. Figure 8 shows the results for a 5-cycle-per- 

 second difference between the two frequencies. Negative values of 

 time indicate that the path was cleared before the beginning of the 

 wave, and these occur only with the Type A vodas due to the delay 

 circuit. The curves for frequency differences of less than 5 cycles 

 per second show more clipping and greater differences between the 

 devices, while those for greater frequency differences show less time 

 clipped and less difference between the two types of vodas. In the 

 case of weak waves it is evident that the syllabic will give less clipping 



40 



36 



28 



12 



-26 -24 -22 



-20 -18 -16 -14 -12 -10 -8 -6 

 INPUT IN DECIBELS (RELATIVE TO I MILLIWATT) 



Fig. 7 — Vodas operating times with sine waves suddenly applied. 



because the energy of the wave does not rise to the value required to 

 operate the Type A device until after the syllabic device has operated; 

 and for very weak waves the Type A does not operate at all. In the 

 case of strong waves, the Type A vodas is better due to its delay 

 circuit. However, since the clipped time is greater on weak sounds 

 than on strong ones, the two types give performances on speech which 

 are judged to be equivalent. 



A comparison of operation of the two types of vodas on a speech 

 wave is shown in Fig. 9. Reading from left to right, the middle trace 

 of this oscillogram shows the wave recorded by saying the word 



