109-4 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1952 



confusing to customers and that consequently there would be an exces- 

 sive number of dialing errors. It was therefore planned to use semi- 

 mechanical operation for cities like New York, retaining an operator 

 between the customer and the machine. While this scheme did not save 

 as many operators as the full mechanical method, it was believed neces- 

 sary to have trained operators so that the customers would not be sub- 

 jected to the complications of dialing. Under the proposed arrangement, 

 the customer would pass the office name and number orally, and the 

 operator would substitute the dial code for the office name and key or 

 dial the code and number into the machine. Trial installations of the 

 semi-mechanical panel system placed in service in the Waverly and 

 Mulberry offices, Newark, N. J., in 1915 demonstrated that this method 

 could provide reliable and improved telephone service under severe 

 conditions. 



However, in 1917 W. G. Blauvelt of the American Telephone and Tele- 

 graph Company proposed a numbering plan which would permit the cus- 

 tomer to dial up to seven digits with acceptable accuracy and which 

 would also be satisfactory for manual operation. This arrangement con- 

 sisted of the use of one to three letters and four numbers. The first one, 

 two or three letters of the office name were printed in bold type in the 

 directory as an indication to dial customers that these were to be dialed 

 ahead of the four numbers. Manual customers used the office name as be- 

 fore. Letters as well as numbers were placed on the dial plate in line with 

 the finger holes of the dial. This proposal was immediately adopted and 

 further Bell System development proceeded along the lines of full auto- 

 matic operation. The Bell System planned to use the panel system in large 

 cities not only because of the trunk efficiency which was possible with the 

 use of the large panel switch, but also because trunking, being no longer 

 under direct control of the dial in this system, was divorced from num- 

 bering. The panel system was also attractive because it had flexibility for 

 growth and for contingencies such as the introduction of new types of 

 service. These advantages would be provided by the common senders and 

 translators of that system. 



EARLY INSTALLATIONS OF COMMON CONTROL SYSTEMS 



Early in 1918 tentative schedules were set up for 6-digit panel offices 

 for Kansas City and Omaha and late that year a 7-digit office was recom- 

 mended for the Pennsylvania office in New York City. When the Atlantic 

 office in Omaha w^as placed in service on Dec. 10, 1921, it became the 

 first commercial installation of a full automatic panel system. 



Commercial installations of rotary equipment preceded the first com- 



