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BELL SYSTEM TECHNICAL JOURNAL 



case where the volume of each of the active channels is controlled so 

 as to be 12.1 db below reference volume. The choice of this particular 

 volume is purely arbitrary, but it corresponds to the average power of 

 the single talker volume distribution. 



The equivalent volumes given by curve A of Fig. 6 are a measure 

 of the average power of the N channels, as computed by means of 

 equation (2). To determine the required instantaneous load capacity 

 of the system, the average power must be corrected by the multi- 

 channel peak factor which is read directly from Fig. 4, using for the 

 number of active channels the values read from Fig. 5. 



For design purposes, it is more convenient to use the rms power 

 of the single frequency test tone whose peak value represents the 



5 10 50 100 500 1000 



NUMBER OF CHANNELS IN SYSTEM (n) 



Fig. 7 — Load capacity for systems of N channels. 



instantaneous load capacity. As the ratio of the peak to rms power of 

 a single frequency tone is 3 db, this test power is obtained by subtract- 

 ing 3 db from the instantaneous load capacity. This required test- 

 tone capacity is plotted as a function of N in curve A of Fig. 7, which 

 gives the output capacity required for an iV-channel system with 

 volume control as specified above. 



Uncontrolled Volumes 



For systems in which volume control is not used, the application 



of this procedure becomes more involved. To study this more general 



case, it is convenient first to interchange the conditions of the preceding 



section, letting the number of active channels be fixed at any value n 



