34 



THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1952 



finders left in service was adjusted in order to obtain a reasonable num- 

 ber of dial tone delays in the next half hour without producing a severe 

 reaction from the subscribers served by the line groups under study. 

 The data recorded on the tapes showed continuously the busy or idle 

 conditions of certain circuits associated with the line groups under 

 study. In some cases the receipt of dial pulses and the operation of 

 registers were also recorded. These circuits included line finders, a few 

 subscriber fines, trip circuit sub-groups, the all trunks busy register, 

 the peg count register and the speed of dial tone measuring device. In 



Table I 



Maximum 



Percent 



Dial Tone 



Delays Over 



3 Seconds 



Message rate individual 



Morning tapes 



Afternoon tapes 



Message rate two-party 



Morning tapes 



Afternoon tapes 



Evening tapes 



Flat rate individual ... 



Morning tapes 



Afternoon tapes 



Coin 



Morning tapes 



Afternoon tapes 



Evening tapes 



53.3 

 55.6 



40.0 

 88.6 

 71.2 



48.9 

 35.6 



71.1 

 35.6 

 68.9 



addition the busy and idle conditions of a sample of senders was ob- 

 served in order to note the general load level on the senders. 



RELATIONSHIP BETWEEN LOAD CARRIED AND PER CENT DIAL TONE DELAY 



One of the principal objectives of these tests was to establish as far 

 as possible the relationship between the average load carried by a line- 

 finder group and the corresponding dial tone service when there is a 

 shortage of line finders but not of senders.^ The average load carried 

 was obtained by making a switch count every thirty seconds of the 

 number of line finders busy as indicated by the 100-pen recorder tape. 

 The dial tone tests were made with the speed of dial tone measuring 

 device. Forty-five dial tone tests were made each half hour for each 



' The restriction of avoiding dial-tone delays due to a sender shortage was to 

 eliminate a factor external to the line-finder group and to make the results of the 

 tests applicable to both common-control and non-common-control type dial 

 systems. 



