472 



THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 195G 



dividual OST groups is within the limits one might expect for data 

 based on single-hour observations and for which the magnitudes of the 

 direct group offered loads required some estimation. The assumption of 

 random traffic offered to the OST gives, as anticipated, loss predictions 

 (Erlang £"1) consistently below those observed. 



More recently extensive field tests have been conducted on a working 

 toll automatic alternate route system at Newark, New Jersey. High 

 usage groups to seven distant large cities o\'erflowed calls to the New- 

 ark-Pittsburgh alternate (final) route. Data describing the high usage 

 groups and typical system busy hoiu- loads are given in Table ^T. (The 

 loads, of course, varied considerably from day to day.) The size of the 

 Pittsburgh route varied over the six weeks of the 1955 tests from 64 to 

 71 trunks. Altogether the system comprised some 255 intertoll trunks. 



Observations were made at the Newark end of the groups by means 

 of a Traffic Usage Recorder — making switch counts every 100 seconds 

 — and by peg count and o^'erflow registers. Register readings were photo- 

 graphically recorded by half-hourly, or more frequent, intervals. To 



^- 



<a 

 uz 



^^ 

 zz 



05 



1-0 



(T-l 

 °^ 



1.0 



0.5 



0.2 



2 0.1 



0.05 



0.02 



0.01 



LOAD |vAR 13.58 15.66 6.59 7.30 2.51 18.54 2.77 4.59 5.90 



Fig. 30 — -Observed tandem ovciflow.s in nlicriKilc 

 llill-2 (New York) 1940-1941. 



loulc study at Murray 



