DIALING BEHAVIOR OF SUBSCRIBERS 



445 



The ratios of overflows to attempts compared with theoretical results for 

 the Poisson and Erlang B formulae for 153 CCS of offered traffic are as 

 follows: 



Table VI 



The ratios of overflows to attempts are apparently very close to the 

 Poisson results. No further conclusion should be drawn from this, at this 

 time, without further study. 



Summary 



Data concerning the dialing behavior of subscribers who encounter busies 

 have been obtained for New York City subscribers. These data indicate 

 quantitatively: (1) how soon after obtaining a busy, a subscriber redials his 

 call; (2) what percentage of subscribers make subsequent attempts; and 

 (3) the pattern of time intervals between successive subsequent attempts. 

 These data appear to have direct application in the development of trunk 

 capacity tables for trunks handling subscriber-dialed traffic when trunk 

 shortages occur. 



Acknowledgments 



The writer gratefully acknowledges the help of Mr. H. P. Penny in plan- 

 ning the method for taking the service observations and in taking the 

 Manhattan and Bronx- Westchester observations. The help of Mr. R. A. 

 Colbeth is acknowledged in taking the Brooklyn-Queens observations. 



