SWITCHING PLAN FOR TELEPHONE TOLL SERVICE 447 



A second, and it is believed more promising general trend would 

 result from the gradual increase in the number of regional centers as 

 the continued development of business makes this economical. With 

 this growth would come also a continued increase in the number of 

 toll centers connected directly to a regional center. By this process 

 there would be a continued growth in the number of toll centers 

 which can be interconnected with a maximum of two intermediate 

 switches, and it is possible that ultimately the primary outlets can 

 drop out of the picture completely, giving a maximum of two inter- 

 mediate switches for the entire country. While any such outcome is 

 evidently many years away, it seems probable that it is along these 

 lines the growth in development of the plan should be directed. 



Although this direction of development avoids the congestion which 

 would be brought about by the single regional center plan, even under 

 this plan the rapidly growing amount of toll switching to be done in 

 large metropolitan centers offers a very important problem for the 

 future. Toll switching at these points is rapidly outgrowing the 

 capacity of a single manual switchboard, as the switching of local 

 calls did long ago. Equipment changes are being made which increase 

 this capacity, but they can be but a temporary relief. Looking to 

 the future, an increasing amount of the outgoing traffic will be handled 

 by operators in the local central offices, reaching the toll line over 

 toll tandem trunks. It is evident, however, that the ultimate solution 

 of the problem will involve the use of machine methods for the selection 

 of the toll line by the operators, as is now done in certain segregated 

 toll tandem systems. 



The entire trend of recent years is thus to decrease the differences 

 between the handling of exchange messages and of toll messages. 

 At the present time more than 95 per cent of the toll messages are 

 completed while the subscriber remains at the telephone, with speeds 

 of completion only slightly slower than those of exchange messages. 

 Transmission standards, while naturally somewhat better for the 

 shorter distances involved in exchange messages, are, nevertheless, 

 rapidly becoming very comparable. The present view of trends for 

 the future is for continuation of this process, perhaps even to the use 

 of similar types of machine equipment at central offices for switching 

 the various classes of messages. 



The author gratefully acknowledges the assistance of many of his 

 associates in the preparation of this paper, and particularly of Mr. 

 J. V. Dunn. 



