68 



THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1953 



Table III — Formulas for /, Probability of Interference 



n = Number of consecutive channels in available band, 

 p = Number of operating channels picked at random from those in band. 

 T = Portion of time average channel is activated by transmitter. 

 m = Number of intermodulation products of a specific type expected to 

 fall within band of n channels when pT channels are activated. 



Type of Intermodulation 



2A - B 

 A + B - C 

 ZA - 2B 

 ZA - B - C 

 2A+ B - 2C 

 2A-\- B - C - D 

 A + B + C -2D 

 A+B+C-D-E 



Formula for m 



mi 



nh 



Tlli 



^ pT{pT - l)(n - 2) 



2(n - 1) 



^ pTjpT - l){pT - 2)(2n - 5) 

 6(n ~ 1) 



^ pTjpT - l)(n - 2) 



n{n - l)(n - 2)(n - 3)(n - 4) 



I — -] when only third order products are considered. 



/"I— (1 j when both third and fifth order products are 



conaidered. 



