these considerations, the telephone toll plant and service offer very- 

 good examples of the advantages of standardization in plant and in 

 operating methods. 



The complexity of the toll plant and the number of types of appa- 

 ratus and material which would be required would be greatly multiplied 

 if it were not for the high degree of standardization in the Bell System 

 telephone plant. In fact, it is not an exaggeration to say that the 

 telephone toll service of today could not be given had not effective 

 steps been taken from the beginning looking to this high degree of 

 standardization and simplification. 



Plant Design 



It is evident that if each toll circuit were designed individually to 

 meet exactly the requirements for that circuit as regards efficiency for 

 good transmission and other requirements, the result would be, in 

 general, that each small group of toll circuits between two points 

 would differ in electrical design from every other group of toll circuits 

 between any other two points. This would result in many thousands 

 of different kinds of toll facilities, each designed for a specific use only, 

 and would result in endless confusion and lack of practicability. How- 

 ever, the standardization of the apparatus and materials forming the 

 toll telephone plant has been carried on since the beginning of toll 

 service and has resulted in a simplification of practice and the general 

 use of the same types of apparatus and material throughout the 

 country. For example, there has been a high degree of standardiza- 

 tion of the sizes of copper wire used for open-wire telephone conductors. 

 A very large percentage of the wire used in the plant for this purpose 

 is made up of three sizes, respectively, 104, 128, and 168 mils in 

 diameter. In toll cables, practically all conductors are made up 

 entirely of two gauges, 16 and 19 B & S gauge. With few exceptions, 

 repeaters for telephone message circuits are of either one of two basic 

 types, one for two-wire circuits and one for four-wire circuits, with 

 such modifications in balancing arrangements, signaling arrangements, 

 etc., as are necessary to adapt them to the different types of circuit. 

 Carrier systems are one of two general types, a three-channel system 

 for long distances and a single-channel system for shorter distances, 

 although additional types of system for other types of circuit condition 

 are now under development. In the design of any given circuit, 

 choice is made from this limited number of types of facilities, selecting 

 the one which will give not less than the required transmission efficiency 

 in the given case with maximum economy and other advantages. This 

 procedure results in great advantages in simplicity of plant design and 



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