| 释义 |
NXX as 0 or 1 would confuse the network, and X indicating that any number is allowed. A call within an area code requires that the caller enter only the CO prefix and the line number, i.e., NXX.xxxx, unless there is an overlay area code. The line number can consist of any four digits (xxxx), and corresponds with a port on a switch that connects to a circuit or channel over a local loop that serves the physical premises of a subscriber. In the case of a cellular telephone number, there is no local loop, as such, and the number is associated with a handset, rather than a physical premises. See also CO, CSA, GSTN, NANP, overlay area code, and PSTN. |