DIALING HABITS OF TELEPHONE CUSTOMERS 



55 



The observer was provided with a means for introducing either no 

 delay or one of four values of delay 2, 5, 10 or 15 seconds into the sender 

 dial tone circuit. The observer took 50 observations using a particular 

 value of dial tone delay and then shifted to another so that no particu- 

 lar value of delay would become evident to the customers during an 

 afternoon's test. Each group of 50 observations comprised a mixture of 

 message rate, coin and flat rate calls in the approximate proportions of 

 13 to 6 to 1, representing the respective volumes of traffic from these 

 classes of service during the afternoon periods. It was not possible to 

 distinguish PBX lines or two-party lines from the bulk of the message 

 rate data nor PBX lines in the flat rate data, although to a limited 

 extent the observer could identify PBX dialing by the generally faster 

 pulsing. The coin data represent both public and semi-public customers. 



Fig. 12 is a diagram for explaining the results shown on Figs. 13, 14 

 and 15 for the message rate, flat rate and coin classes of service, respec- 

 tively as obtained with the sender monitoring circuit. Fig. 12 was ob- 

 tained by the application of fitting curves to those message rate data of 

 Fig. 13 for which a dial tone delay of five seconds was introduced by the 

 observer. In the interval from t = to t = 5 seconds, three curves A, B 

 and C represent the per cent of subscribers still waiting at time t for dial 

 tone. Curve A and its extension beyond t = 5 seconds represents the 

 action of subscribers who would dial their calls before tone if dial tone 

 were delayed indefinitely. Curve B and its extension beyond t = 5 



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2 4 6 8 10 12 14 



TIME,t, IN SECONDS AFTER SENDER SEIZURE 



Fig. 12 — Explanatorj' chart for sender monitoring observations; dial tone at 

 T = 5 seconds. 



