| 单词 | area code |
| 释义 | area code Also known as the Numbering Plan Area (NPA). In the North American Numbering Plan (NANP), the three-digit number that corresponds to a geographic area within the area loosely defined as North America.The NPA follows the pattern NXX, with N indicating that only digits 2 9 are allowed, as 0 or 1 would confuse the network, and X indicating that any digit is allowed.The area code originally was used only when a call crossed an area code boundary. In such a case, the dialing sequence is 1.NNX.NNX.xxxx. the 1+ identified the call as long distance and triggered the involvement of an interexchange carrier.Where overlay area codes have been implemented, however, it is necessary to dial a full 10-digit number (NNX.NNX. xxxx) within a geographic area.Also, cellular networks treat area codes differently in terms of dialing pattern and rating. Cellular networks do not require 1+ dialing, and generally 74570c01.qxd 9/12/07 12:34 AM Page 38 |
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