INTKKTOLL TUl \K CONX'ENTRATING EQUIPMENT 327 



However, it shouhl he lenieinbcrecl that it contains a single controller 

 which could he ciisal)le(l hy compound Irouhle, a condition which could 

 he .serious if the concentratin<>; (Miuipinent were the sole means of handling 

 traffic from any switchljoard. It is intended that the concentrating equip- 

 ment he used in conjunction with direct intertoll circuits and/or tandem 

 ti'unks to a Xo. 4 type toll crossbar switching system. When used with 

 direct circuits an operator alternate routing system ensues. Referring 

 back to the paragraph which dealt with idle trunk indicating, it is noted 

 that the direct trunks and tlie concentrator tnuiks form a single group 

 or subgroup of trunks to a common destination. The direct trunks appeal' 

 in the multiple at the head end of the group and are followed by con- 

 centrator trunks. The idle indicating lamps direct the operator to a 

 direct trunk, when available, as first choice, and automatically direct 

 the operator to a concentrator trunk when the direct trunks are in use. 

 If the operator also has access to trunks to the toll crossbar office these 

 trunks become third choice for use when the direct and concentrator 

 trunks are busy. Fig. 14 illustrates this situation. The concentrating 

 eciuipment may be located apart from the central toll building without 

 losing the advantages of the alternate routing discussed above. Thus it 

 is available for dispersing the toll plant to minimize the ef!'ect of disaster. 



A CKNOWLEDGMENT 



The development of the Intertoll Trunk Concentrating Equipment was 

 the combined effort of many people. Important contributions were made 

 by M. Posin and W. L. Shafer, Jr. 



