INTERTOLL TRUNK CONCKXTRATIXG EQUIPMENT 305 



CLiits only via tandem trunks to the No. 4 type toll crossbar office in the 

 home toll center. 



Handling such trafhc tiu'ouu;h llu> toll ci'ossbar oflici' involves greater 

 operating effort than handling it hy direct trunks since three additional 

 digits per call must be keyed by the operator to direct the call through 

 the toll crossbar office. Also the cost for an intertoU connection is higher 

 with the tandem trunk method than with the direct circuit method, due 

 to the greater number of switching facilities used in establishing the 

 connection. Fig. 1 shows the components used in both cases up to the 

 point wh(M'(^ they join common facilities. 



INTERTOLL TRUNK CONCENTRATING EQUIPMENT 



General 



The intertoU trvmk concentrating equipment has been developed to 

 provide the eciuivalent of direct access to intertoU trunks for the traffic, 

 from individual outward toll switchboards, which cannot justify the use 

 of direct trunks. It is a small special purpose common control type 

 switching system located at a central point. It gathers small traffic loads, 

 to a specific destination and automatically routes this traffic to a com- 

 mon group of intertoU trunk circuits which terminate in a toll or tandem 

 crossbar office in the distant toll center. 



The maximum capacity of a trunk concentrating equipment is 100 

 incoming trunks and 40 outgoing trunks. It may be furnished in smaller 

 sizes. If more than 40 outgoing trunks are required to a particular 

 destination, additional concentrating equipments may be furnished. 



The field of use for this equipment lies between that of direct trunks 

 and trunks reached through the toll crossbar switching system. 



The concentrating equipment is arranged only for multifi-eciuency 

 pulsing from the switchboard. This is a system of pulsing in which com- 

 binations of two frequencies within the; voice frequency band are trans- 

 mitted over the talking path to the distant end. Each digit from to 9 

 employs a different pair of freciueiicies. 



The intertoU trunk concentrating eciuipment consists of 4 basic circuit 

 components, namely, incoming trunk, trunk selection switches, controller 

 and outgoing trunk circuits. 



The detached contact form of circuit, prc^sentation is employed in the 

 figures because of its simplicity. In this method the core and winding of 

 a relay may be shown in one location and the associated contacts in other 

 convenient locations. The core and contacts are related by the common 

 designation which appears at the symbols which represent them. 



