THROWDOWN MACHINE FOR TRAFFIC STUDIES 



311 



It was also found that approximately 90% of the partial dials and the 

 abandoned no dials were reoriginated. These percentages are quoted 

 only to illustrate subscriber behavior under certain conditions of cen- 

 tral office load at a particular office. Type of service, load conditions 

 on the central office, and location can effect these percentages. For a 

 more detailed analysis, see "Dialing Habits of Telephone Customers."* 



Fig. 6 illustrates only the group behavior of subscribers. Individually, 

 the subscribers will hold equipment on abandoned no dials, abandoned 

 partial dials, and false starts for varying amounts of time. These varying 

 individual holding times can be quantized into several average values 

 which are equally likely to occur, or may be averaged to one value as 

 shown on Fig. 6 depending upon the throwdown study requirements. 

 The holding times on calls receiving tone are usually assumed to cease 

 a few seconds after tone is received. 



Subscribers, as indi\'iduals placing ultimate good calls, spend varying 

 amounts of time, after receipt of dial tone, before start of dialing and 



INITIAL SUBSCRIBER STARTS 



GOOD CALLS 



FALSE STARTS 



ALL END WITHIN TWO SECONDS 

 AFTER DIAL TONE IS RECEIVED 



NOT REORIGINATED 



NO DIALS 



PARTIAL DIALS 



RECEIVE 



TONE AFTER 



TIME-OUT 



ABANDONED BY 



SUBSCRIBER BEFORE 



TIME-OUT TONE 



RECEIVE 



TONE AFTER 



TIME-OUT 



ABANDONED 



BEFORE 



TIME-OUT TONE 



HELD W 

 SECONDS 



HELD X* 

 SECONDS 



i 1 



NOT REORIGINATED 



HELD y 

 SECONDS 



REORIGINATED 



HELD p 

 SECONDS 



HELD a^ 

 SECONDS 



I i 



REORIGINATED 



r I 



HELD Z 

 SECONDS 



REORIGINATED 



*UNDER CONDITIONS 

 OF ALL REGISTERS BUSY 

 IN THE NO. 5 SWITCHING 

 SYSTEM, THE TIME-OUT PERIOD 

 IS AUTOMATICALLY DECREASED 



ULTIMATE GOOD CALLS 



Fig. 6 — Simplified characteristic action of subscribers in converting initial 

 subscriber starts to ultimate good calls. 



* Charles Clos and Roger I. Wilkinson, "Dialing Habits of Telephone Cus- 

 tomers," Bell System Tech. J., 31, pp. 32-67, Jan. 1952. 



