854 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1952 



Under operator toll dialing the inward operator is replaced by dial 

 switching equipment under the control of the outward operator; hence 

 the outward operator has no one to rely upon but herself in completing a 

 toll connection to a distant city. With the present method the operator 

 dials a code for each circuit group in the connection followed by the 

 number of the called party which may consist of any number of digits 

 from three to seven. The operator must refer to her position bulletin or 

 to a routing operator for the correct circuit group codes unless she hap- 

 pens to remember them. Where the office to be reached has central office 

 names, the operator must rely on routing information to determine how 

 many letters of the name are to be dialed. The great variation in the 

 number of digits to be dialed on different calls is a source of some dif- 

 ficulty and confusion to the operators. 



The present system of operator toll dialing by which operators use 

 codes depending upon the routes to reach a desired destination, is a 

 great improvement over the old manual handling methods. However, 

 with the introduction of more modern toll switching facilities and the 

 nationwide extension of toll dialing, it was realized that an improvement 

 in the methods for dialing toll calls to distant cities was essential in order 

 to realize the maximum speed and accuracy inherent in toll dialing. 



These handicaps in the present toll dialing methods are to be overcome 

 by establishing a nationwide numbering plan covering the United States 

 and Canada by which each of the more than 20,000 central offices in the 

 two countries is to be given a distinctive designation which identifies 

 that particular office and that office only. This designation is to consist of 



Table I — Different Types of Numbering Plans 



