Direct dating telephone number
Telephone numbers are entered or dialed by a calling party on the originating telephone set, which transmits the sequence of digits in the process of signaling to a telephone exchange.
The exchange completes the call either to another locally connected subscriber or via the PSTN to the called party.
For example, a telephone number in North America consists of a three-digit area code, a three-digit central office code, and four digits for the line number.
If the area has no area code overlays or if the provider allows it, seven-digit dialing may be permissible for calls within the area, but some areas have implemented mandatory ten-digit dialing.
In addition to telephones, they have been used to access other devices, such as computer modems, pagers, and fax machines.
With landlines, modems and pagers falling out of use in favor of all-digital always-connected broadband Internet and mobile phones, telephone numbers are now often used by data-only cellular devices, such as some tablet computers, digital televisions, video game controllers, and mobile hotspots, on which it is not even possible to make or accept a call.
This code specifies that the entire number should be 15 digits or shorter, and begin with a country prefix.Most countries use fixed-length numbers (for normal lines at least) and therefore the number of endpoints determines the necessary length of the telephone number.It is also possible for each subscriber to have a set of shorter numbers for the endpoints most often used.The number contains the information necessary to identify uniquely the intended endpoint for the telephone call.Each such endpoint must have a unique number within the public switched telephone network.