COMMON CONTUOI. .SWlTL'illNG SYSTEMS UMi 



opiMators i(Hiuiro{l ])y an amount iaiifi;iiig- iVoin 30 to 50 per cent l)y 

 eliminating the "B" operators and increasing the efiiciency of tlie "A" 

 operators. At that time, full automatic systems were subject to a nunilxi 

 of shortcomings such as (he comj)lications and uiu-eHabiHty of liie i)ulsing 

 de\-ice at tlie subscriber's station, tlie need for a local battery at the 

 station, and the lack of arrangements for party line and message latc 

 service. Furthermore, there was considerable doubt as to the ability of 

 the .subscriber to dial with acceptable accuracy the si.\ or seven mmierical 

 digits required in some of the multi-offiee exchanges. 



There was an acute need for relief from the difficulties of manual 

 operation after the start of World War I. Telephone growth was so rapid 

 that it appeared for a time that the demand for new operators, ])articu- 

 larly in the large cities, might outstrip the availal)le supply. Comjx'tition 

 fi'om other industry for female help was also increasing. As mor(> offices 

 were added, the situation was further aggravated by the increasing com- 

 plexity of operation. On account of the increasing number of trnnkcd 

 calls, the growing number of central offices, and the increasing amount 

 of manual tandem operation, the ciuality of service was being degraded. 



DEVELOPMENT OF A LARGE CITY NUMBERING PLAN 



By 191G, the full automatic system (Strowger) had established a 

 competitive position with manual for single-office cities, and both manual 

 and full automatic offices were considered to be more economical than 

 semi-mechanical for such cities. Because the number of dial pulls for a 

 single office was four or less, little concern was felt about dialing accuracy. 



For the multi-office cities it appeared that full mechanical operation 

 would improve service and be more economical than either the semi- 

 mechanical sj'stem or manual and would reduce the pressing need for 

 operators. However, in spite of these factors urging the adoption of a dial 

 system and even though automatic equipment was actually used in Los 

 Angeles and Chicago in the first decade of the century, there w^as a 

 reluctance to adopt full automatic operation in the very large multi-office 

 cities because of the lack of a suitable numbering plan. A cumbersome 

 plan was under consideration for handling dial traffic in these cities. This 

 required the use of seven-digit numbei's with the dial customers being 

 called on to use arbitrary three-digit numerical codes for the office 

 names. At the same time, the existing office names would be retained 

 for use by the manual customers. Adoption of this dual tirrangement 

 would have required the provision of a cumbersome directoiy, but worse 

 than that, it was felt that dialing seven numerical digits would be too 



