File:Bell telephone magazine (1922) (14570353027).jpg

Identifier: belltelephonemag26amerrich (find matches)
Title: Bell telephone magazine
Year: 1922 (1920s)
Authors: American Telephone and Telegraph Company American Telephone and Telegraph Company. Information Dept
Subjects: Telephone
Publisher: (New York, American Telephone and Telegraph Co., etc.)
Contributing Library: Prelinger Library
Digitizing Sponsor: Internet Archive

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et in this way: TheUnited States and Can-ada will be divided into82 numbering-plan areasand, where practical,these areas will includean entire state or prov-ince. Each area will in-clude up to approxi-mately 500 central of-fices, and each office willbe assigned a three-digitrouting code which doesnot conflict with anyother routing code in itsarea. Each numbering-plan area will itself be reached bymeans of a three-digit code that doesnot conflict with any other area codeor with any central-office routingcode (see page 188). Thus, each central office in thiscountry and in Canada will be desig-nated by six digits which will dis-tinguish it from every other centraloffice in the two countries. A maxi-mum of ten digits dialed by the origi-nating operator will reach any tele-phone : three digits for the area code,three digits for the central-officecode, and four digits for the calledline number. The few exceptions tothis ten-digit standard include princi-pally the party-line designations and
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Installation pj-ogresses:/rafnes 0/ crossbarequipment at the left three-digit central office numbers. Tochange these would, of course, resultin considerable expense and annoy-ance to telephone customers. Now let us look at the make-up ofthe codes themselves. In the BellSystem, and in many of the independ-ent telephone companies, o (zero)is reserved as a special code by whicha customer reaches the operator.Zero therefore is not available asthe first digit of a routing code. Thefigure i (one) is avoided as a firstdigit of a code because our equipmentis arranged so that an initial pulse ofi is ineffective. These figures,o and i, are not used in central-office names and there are no letters i86 Bell Telephone Magazine WINTER on the dials in the o and i posi-tions. (You may have noticed thatin some places the dial number platehas the letter z in the o posi-tion, but it is not used as part of acentral-office name.) Just because we cannot use themto start a central-office code, how-ever, doe

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