r.xuiM I ki.m; /'A'( •/(/./ .u.v or iiii. ini.i. svsir.M 5.»5 



pri>|H'r rt'nistr.ilion !>>■ llu- in.i«liiiu' .iiid tin- nu'ch.iiiisiii is so .irr.iiim'd. 

 tlu'rff«)rf, that on tlu' nimpUlion of tlir call it will ti-sl tlif iiiu' to makt- 

 sure that i-viTsthiiiK was normal iK-fori- rinislration is actually ptr- 

 fornu'd. Similarly, all the way thronnh the completion of the regular 

 anil special classes of calls it is necessary for the mechanism lo perform 

 just such intric.ite functions as that descrihed. 



The eiigiiieerinn of the interotTice trunk la\<>ul in a ciiy like New 

 \'ork is also an im|)ortant and interesting; problem, not only hec.iiisi' 

 of its m.ignitude l)ul because of the almost unlimited \arialions which 



EXCHANGE TRUNKING PLANS 



TRUNK GROUPS RCQWREO BETWCEN TEN CENTRAL OFflCES 



OlRCCt TRUNK PLAM TANOCU TRUNK PLAN 



90 CROUPS JO goouPS 



AMDCM AND DIRCCT 

 TRUNK PLAN 

 50 GROUPS 



NEW YORK METROPOLITAN ATCA 



TRUNK 6R0UP3 REQUIRED 



OlflCCT TRUNK PLAN TAND£M TRUNK PLAN TANDCM AND DIRCCT 



TRUNK PLAN 

 'aOOO 6R0UPS 850 GROUPS aSOO GROUPS 



FiR. 12 



might he empl(>\ed, a large number ol which must be carefuih' con- 

 siderc<l in connection with ailditions to the plant. In opening new 

 central oftices, trunk circuits must be pro\ided between each new office 

 and the existing offices and also between the new offices themselves. 



Fig. 12 illustrates the range of trunking layouts which might be 

 used. With the 10 offices assumed and direct trunks between each 

 office and every other ofitice, 00 groups of trunks would be required. 

 With the so-called full tandem operation; that is, under an arrange- 

 ment whereby each office reaches every other office through a central 

 point, 20 groups of trunks would be required. Between these two 

 extremes with some offices reaching certain other offices through the 

 tandem center and certain others by direct trunks, a great many 

 combinations would be possible. In the case assumed 50 groups 

 app>eared to be the best combination. The data given at the bottom 

 of Fig. 12 are of particular interest in this connection. As will be 



