telephone exchange number; telephone prefix
Telecommunications term for the exchange-code or prefix part of a telephone number. It is especially common in compounds such as 市外局番 and 市内局番.
この地域では来月から電話の局番が変わります。
In this area, the telephone exchange number will change next month.
市外局番を忘れずに入力してください。
Please be sure to enter the area code.
The exchange code for this area is 03.
When calling outside the area, please dial starting with the exchange code.