<P> A long distance call within the same area code could often be dialed as 1 + 7D, without using an area code . The scheme relied on the second digit of an area code being 0 - 1 and the second digit of a local exchange being 2 - 9 . This dialing plan was broken by the introduction of area code 334 and area code 360 in 1995 . </P> <P> Traditionally, identical central office codes in adjacent Numbering Plan Areas (NPAs) would be assigned as far apart from each other as possible, so that callers living near an NPA boundary would not confuse numbers in the adjacent NPAs . Central office code protection made it possible in some low density areas to use seven digits to reach areas in another area code, such as Hull from Ottawa before 2006, as every Ottawa - Hull local number originally was reserved in both area code 613 and 819 . </P> <P> Area code overlay plans introduced a requirement in most areas that all calls, even local, must include the area code, resulting in the term 10 - digit dialing . Seven - digit calling is still possible in those numbering plan areas of North America not subject to an overlay plan . </P> <P> Traditionally, calling from one area code to another, specifically for long distance calls, requires the caller to dial the trunk digit "1" before the code and number . More recently, with the increasing number and decreasing geographic size of area codes, it is increasingly possible to call a number in another area code that is not long distance where such a call does require the area code, but not the trunk digit (initial "1"). </P>

When did phone numbers go to 7 digits