TRENDS IN PRACTISE AS AFFECTING COORDINATION 161 



This trend is the steady improvement in the quaHty of service afforded 

 to their customers. 



In the telephone system the improvement in the standards of service, 

 if considered by itself, tends to increase the noticeability and the re- 

 action on service of inductive effects from outside sources. Such 

 changes as the improvement in the characteristics of transmitted 

 speech, including the extension of the band of frequencies efficiently 

 transmitted, and the avoidance of cases in which interfering noises 

 are produced from sources within the telephone plant, tend to increase 



9 IS 



Fig. 2 — Telephone station and power customer growth. 



Note: Values for 1930 are estimates based on best available data, 

 data refer to Bell System. 



Telephone 



the effect of moderate amounts of noise current induced in the tele- 

 phone circuits from outside sources. Similarly increases in the extent 

 of the service and in the speed of completing calls have led to increased 

 reliance on prompt telephone communication which tends to increase 

 the importance of avoiding interruptions. Five years ago the average 

 interval of time between the placing of a long-distance toll call by a 

 subscriber and the commencing of the conversation was 1)4 minutes. 

 At the present time it is a little less than 2>^ minutes. Telephone 

 users have now come to rely on the almost immediate establishment of 

 telephone connections and are correspondingly more critical of inter- 

 ruptions or delays. 



