įor automatic telephone service, impulse senders ( dials) were installed on customer telephones, so that subscribers did not need operators to initiate a call, but simply dial the directory number themselves. The selection of central office names was conducted in a careful manner to avoid misunderstanding of the verbal requests. A caller would request a connection to Market 1234, for example. But many cities chose other naming schemes, using locally significant names of districts, parks, or other well-known features, such as Market. Often, additional central offices might be named by the directions of the compass, North, South, East, and West. Cities soon needed additional branch offices some distance from Central, to accommodate the subscriber base and expanding area, as a single office typically served a maximum of ten thousand telephone numbers. Single exchanges ( central offices) were typically named after the municipality or location, so that calls to another town could be easily identified. While this method persisted into the 1920s in very small communities, growth of the business soon made this impractical, and subscriber stations were assigned telephone numbers. In the early, small telephone networks, it was customary to initiate a connection to another subscriber by requesting the name of desired party from the operator. The telephone number of this station is K-9293 Since the letter K is emboldened, it was a required component of the telephone number, dialed as the digit 5, as the red lettering indicates. Similar developments followed around the world, such as the British all-figure dialling.īackground This mid- to late-1950s telephone dial displays the name of telephone exchange Kenmore, in the South Side of Fort Wayne, Indiana. In the United States, the demand for telephone service outpaced the scalability of the alphanumeric system and after introduction of area codes for direct-distance dialing, all-number calling became necessary. Telephone exchange names were used in many countries, but were phased out in favor of numeric systems in the 1960s. On the number card of the telephone instrument, the name was typically shown in full, but only the significant letters to be dialed were capitalized, while the rest of the name was shown in lower case. Telephone directories or other telephone number displays, such as in advertising, typically listed the telephone number showing the significant letters of the central office name in bold capital letters, followed by the digits that identified the subscriber line. Blauvelt of AT&T proposed a mapping system that displayed three letters each with the digits 2 through 9 on the dial. Such systems were designated as 2L-4N or 2L-5N, or simply 2–4 and 2–5, respectively, but some large cities initially selected plans with three letters ( 3L-4N). A widely used numbering plan was a system of using one or two letters from the central office name with four or five digits. Several systematic telephone numbering plans existed in various communities, typically evolving over time as the subscriber base outgrew older numbering schemes. These letters were mapped to the digits of the dial, which was indicated visibly on the dial's numbering plate. The leading letters of a central office name were used as the leading components of the telephone number representation, so that each telephone number in the area was unique. Central offices were usually identified by names that were locally significant. While small towns and rural areas might each be served by a single exchange, large cities were served by multiple switching systems, either distributed in the community constituting multiple exchange areas, or sometimes hosted in the same building to serve a densely populated area. It identified the switching system to which a telephone was connected, and facilitated the connection of telephone calls between switching systems in different localities. Alphabetic telephone numbering plan Face of a 1939 rotary dial showing the telephone number LA-2697, which includes the first two letters of Lakewood, New JerseyĪ telephone exchange name or central office name was a distinguishing and memorable name assigned to a central office.
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