40 



THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1952 



time from one state to another. By equating certain of these transitions, 

 a series of simultaneous equations evolves, which when solved yields one 

 overall expression. Of interest is the de\'elopment of the transition equa- 

 tions. Thus for a case of c line finders arranged in a simple group, let 

 f(x) represent the probability that x (where x < c) line finders are 

 occupied and /(.r + 1) represent the probability that .r + 1 line finders 

 are occupied. Let n be the a^'erage number of calls offered to the line 

 finders during a long interval of time, T. Let T be the unit of time and h 

 be the average holding time per call measured in terms of T. Over a 



100 



m 90 

 cc 

 O 80 



S 

 70 



(T 



tn 



60 



50 



OBSERVED DIAL TONE TESTER DELAYS 



THEORETICAL DIAL TONE TESTER FITTING CURVE - 

 TEST CALL WAITS ITS TURN IN LINE 



THEORETICAL DIAL TONE TESTER FITTING CURVE - 

 TEST CALL IS ALWAYS FIRST IN LINE 



THEORETICAL DIAL TONE SUBSCRIBER DELAY CURVE 



^. 20 



i S 



^ 7 



(U 



":. 6 



FLAT RATE INDIVIDUAL 

 (10 LINE FINDERS AVAILABLE) 



34 5 6 7 8 9 10 11 



TIME,t. IN SECONDS FROM START OF DIAL TONE TEST 



Fig. 5 — Results of dial tone tests. 



