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In the United States of America, Canada, and other North American Numbering Plan countries, a toll-free telephone number is any number in these area codes: *+1-800 *+1-844 *+1-954 *+1-866 *+1-877 *+1-888 Area codes 1-822 and 1-833 are expected to be used in the future, as well as 1-880 through 1-887 and 1-889. However, 1-811 will not be used, because 8-1-1 has a different meaning. Area code 1-899 is used in Mexico, and also, no area code in North America is currently issued with the middle digit 9 since that number is reserved in case of future expansion. These numbers are free to the caller if dialed from a land-line phone but will incur mobile airtime charges for cellular phones. ==History== Unlike the United Kingdom, most of the United States and all of Canada uses a rate structure in which local calls are flat-rated and incur no per-call cost to residential subscribers. As regulators in North America had long allowed long-distance calling to be priced artificially high over the many decades of Bell System monopoly in return for artificially low rates for local service, subscribers tended to make toll calls rarely and, if they could not be entirely avoided, keep them deliberately brief. A few businesses, eager to sell their products to buyers outside the local calling area, were willing to accept collect calls where they paid the cost of receiving telephone enquiries. Initially, all of these calls had to go through the telephone company's operator, who requested acceptance of the charges for each call manually. An early refinement of this process, in the late 1950s, was for businesses to publish a Zenith number (because, at that time, the letter "Z" was not present on the telephone dial) in various out-of-town directories for towns from which they would accept all charges-reversed calls. This saved a small amount of time, but an operator still had to manually find the underlying number on a printed list and place the call with charges billed to the called party. The first automated toll-free numbers were area code 1–800, created as inbound Wide Area Telephone Service (InWATS) in 1966 (U.S. intrastate) and 1967 (interstate). These terminated on special fixed-rate trunks which would accept calls from a specified calling area with either no limit or a specific maximum number of hours per month. There was no itemised billing of calls and the expensive fixed-rate line was only within financial reach of large corporations and government agencies. In the early 1980s, Bell Labs patented what became AT&T's "Advanced 800 Service" – a computer-controlled system where any toll-free number could point anywhere (such as to a small business local number instead of a special InWATS line) and an itemised bill generated for only the calls the business actually received. By breaking the link between the number's exchange prefix and geographic location, this system opened opportunities for vanity number advertising – an advantage in media like commercial radio where numbers need to be memorable as they're announced only briefly. The toll-free long distance market was opened to competition after 1986 and a RespOrg system instituted in 1993 to provide toll-free number portability between rival carriers using the SMS/800 database. Open competition also brought an end to the pattern of long distance subsidising local service, bringing per-minute charges down to levels where any business could afford to take orders using a 1–800 number. 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「Toll-free telephone numbers in the United States」の詳細全文を読む スポンサード リンク
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