TANDEM OPERATION IN THE BELL SYSTEM 403 



the service to the customer in the large metropolitan areas also has 

 been an important factor. The general introduction of the tandem 

 type of operation on toll board circuits may affect the economic 

 balance, and except where other factors are controlling, will tend to 

 limit the scope of segregated tandem systems of the present type. 

 It may well be that, eventually, in some of the smaller cities the need 

 for a separate tandem system for the local and short-haul toll traffic 

 will disappear altogether. 



Summary 



Tandem systems for local and short-haul toll traffic have been 

 provided : 



1. To reduce the number of trunk groups required in large metro- 



politan areas and to insure maximum efficiency on those pro- 

 vided; due consideration being given, of course, to a proper 

 balance between service and costs. 



2. To permit the same operating and service arrangements on short- 



haul toll traffic as on local traffic, thus facilitating the work 

 of the operators and making the service faster, and easier to 

 use by the customer. 



3. To reduce the cost of handling large volumes of short-haul toll 



traffic through the use of toll plant designed to meet the less 

 exacting transmission requirements, as compared with toll 

 plant used for long distance traffic. 



These systems vary in type, depending upon the types of local 

 central office equipment which are to be interconnected. 



The use of tandem operation in connection with toll board traffic is 

 limited at the present time, but in view of the future volume of this 

 traffic and of new arrangements which now appear feasible, further 

 expansion of the long distance system may be along lines generally 

 similar to those employed in the local and short-haul toll tandem 

 systems; using, of course, operating methods and equipment arrange- 

 ments which adequately meet the requirements on the longer-haul 

 traffic. These new arrangements may involve both dialing and 

 straightforward toll lines. They may affect the economic balance 

 and, thereby, the scope of tandem systems provided heretofore for 

 local and short-haul toll traffic. 



References 



In addition to the paper by Messrs. Wheelock and Jacobsen mentioned on Page 10, 

 certain aspects of tandem operation are referred to in the following papers: 

 1. "General Engineering Problems of the Bell System," H. P. Charlesworth, Bell 

 Sys. Tech. Jour., October, 1925. 



