|
4-1-1 is the telephone number for local directory assistance in the United States and Canada. 4-1-1 is also commonly referred to as "D.A.", "Directory Assistance", or "Information". Approximately 6 billion calls are made to 4-1-1 within the United States every year. 4-1-1 has been used since at least 1930〔New York Telephone Directory for Manhattan, 1930, on film at the NYPL〕 in New York City,〔New York Telephone Directory for Manhattan, 1940, page 1〕 San Francisco,〔San Francisco Bay Telephone Book, 1938, page 3〕 and other large cities where panel and crossbar switching equipment installed by the Bell System was prevalent. However, in smaller Bell System cities and almost all areas served by GTE and other companies where step-by-step equipment was the norm such as Los Angeles,〔Telephone Directory Los Angeles Extended Area, 1938, title page〕 1-1-3 was used until at least the 1960s, and in some cases (the Pacific Northwest, for example) until the mid-1980s. Until the early 1980s, 4-1-1 and 1-1-3 calls were free in most states. In the United States and Canada, Directory Assistance was historically a local function, and most companies updated listings at their directory assistance centers almost daily. Callers would dial 4-1-1 or 1-1-3 for fast, efficient, and accurate service. When long-distance numbers were needed, prior to the full introduction of direct-dialed long-distance service, callers would call either 4-1-1 or "0" (Operator) and request a free long-distance connection to the directory assistance center in the distant city. In 1962 direct-dialed long-distance directory assistance became available. The number in cities with panel and crossbar switching equipment was area code-555-1212, whereas in cities with step-by-step equipment the number was 1-555-1212 (or 112-555-1212) for numbers not local but in the same area code and 1-area code-555-1212 (or 112-area code-555-1212) for numbers in other area codes. In some area codes, the directory assistance center was able to serve the entire area code, but in many, the operator in the principal city of the area code you dialed would connect you onward to a more local directory assistance center for the most up-to-date information. After the introduction of local exchange competition, most telephone companies outsourced directory assistance service to nationwide call centers. This has blurred the distinction between 4-1-1 and 555-1212. For regulatory reasons, where telephone service is provided by traditional local-exchange carriers, the local carrier will determine how to handle 411, your chosen local toll (intra-LATA) carrier will determine how to handle 555-1212 calls for area codes within the LATA, and your chosen long distance carrier for inter-LATA) calls will determine how to handle other area code-555-1212 calls. For service provided by cellular and VoIP carriers where you do not have a choice of local toll or long distance carriers, all calls may be handled the same way. In North America, all areas formerly using 1-1-3 have been converted to using 4-1-1, and 1-1- is now reserved for vertical service codes. Outside North America, "1-1-N" numbers are still in use, for these and other services. In most European countries "1-1-N" numbers are related to emergency services and 112 is the European Unified Emergency Number. ==The relationship between 4-1-1, 1-1-3, and Long Distance Dialing (DDD)== Direct Distance Dialing (DDD) was first introduced in areas with common-control switching (panel and crossbar) in the 1950s. These areas had used 4-1-1 for directory assistance, and because of the ability of common-control switching to analyze the initial digits of a number in a "sender" before routing the call, these areas did not require the dialing of an initial "1" to initiate a long-distance call. There was no ambiguity, because the initial assignment of area codes always used either a "0" or a "1" as the second digit, and the second digit of local numbers was never a "0" or a "1" because of the use of two-letter plus 5-digit local numbering, with the letters only on digits 2-9 of the dial. Areas with step-by-step equipment processed the call one digit at a time as dialed by the caller, and thus needed a common prefix to distinguish long-distance dialing from local calls. The Bell System design choice was "1", but since "1-1-3" was in use for directory assistance, along with other "1-1-" codes ("Repair" was 1-1-4).,〔http://www.atlantatelephonehistory.info/part4.html〕 changes had to be made in the step-by-step areas. Initially, "1-1-2" was used temporarily as the prefix in most of these areas. To simplify long-distance calling it was desirable to change this to a "1". Some areas converted immediately to 4-1-1 for directory assistance and 6-1-1 for repair. Other areas retained 1-1-3 by installing what was known as "double-header" trunks, which actually connected the call to the long distance equipment and then "snatched it back" if the second digit was also a "1". The conversion proceeded as follows in Springfield, Massachusetts: 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「4-1-1」の詳細全文を読む スポンサード リンク
|
