Tiitertoll Trunk Coiiceiitrating Equipment 



By D. F. JOHNSTON 



(Mamisoript leceivcd August 25, 1953) 



This article describes the IntertoU Trunk Concentrating Equipmenl which 

 is a special purpose common-control type switching system. Its function is 

 to combine, at a central point, small groups of trunks serving traffic originat- 

 ing at various outward toll switchboards and to route the combined traffic 

 to a toll or tandem crossbar office in a distant toll center. The operators at 

 the outward toll switchboards are thereby provided with the equivalent of 

 direct access to the intertoll trunk circuits. 



Both operating and equipment savings are realized by the use of this con- 

 centrating equipment as compared to handling the same traffic via a toll 

 crossbar office at the originating toll center. 



INTRODUCTION 



This article deals with a method of handling traffic from outward toll 

 switchboards in a metropolitan toll center to a specific distant toll center 

 with the objectives of (1) providing the efiuivalent of direct access to in- 

 tertoll circuits from the individual switchboards, for traffic for which 

 direct circuits cannot be justified, (2) giving relief to the No. 4 type toll 

 switching system in the metropolitan toll center, and (3) providing a 

 means for the dispersion of toll switching facilities. 



A metropolitan toll center may contain a number of outward toll 

 switchboards. Some of these are situated in the central toll building and 

 others in decentralized locations. An individual outward switchboard 

 may have a sufficient amount of traffic to a sp(!cific distant toll center to 

 justify a group of intertoll circuits direct from the switchboard to the 

 No. 4 type toll or crossbar tandem office in the distant center. It has 

 been the practice to provide such direct access to intertoll circuits at 

 centralized toll switchboards. Traffic exceeding the capacity of such in- 

 tertoll tnuik groups is handled o\-ei- tandem trunks tVoin llie toll switch- 

 boards via tlie No. 4 typ(^ toll crossbar office in the originating center. 

 The decentralized switchboards in general have reached intertoll cir- 



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