possible in some low density areas to use seven digits to reach areas in another area code. Examples: Washington, D.C. (area code 202) to adjacent areas of Maryland (area code 301) and Virginia (area code 703), discontinued on October 1, 1990 to allow assignment of a code in all three area codes. Hull from Ottawa (before 2006, as every Ottawa-Hull local number originally was reserved in both area code 613 and 819). This was terminated on 21 October 2006 to allow assignment of a code in both 613 and 819, although five central office codes associated with the federal government were protected in 819 to allow dialing without potentially reaching non-government lines. Limitations Area code overlay plans introduced a requirement in most areas that calls must include the area code, resulting in a 10-digit dialing requirement. Seven-digit dialing remains possible in some areas of North America. 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 dial 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"). Many modern cellular phones automatically prepend the telephone's own area code if the user enters only seven digits, sending a total of ten digits. This is the same case with many landline providers that allow this. And also with many voice-over-IP services, users can configure default handling of seven-digit dialing in a dial plan. Timeline Before 1947 Local telephone numbers were governed by varying local numbering plans based on historical growth of services. Places without dial service often used special party line syntax (e.g., 2-R-48). The largest cities already used seven-digit numbers. 1947 to 1951 A nationwide numbering plan was announced in 1947, assigning 86 area codes in the United States and Canada. All area codes had a zero or one as the middle digit. A zero indicated that the state or province was served by a single area code. Area codes were initially used to replace trunk routing codes at the toll switching centers in the network for Operator Toll Dialing. Systematic conversion of city dial system commenced to the seven-digit (two-letter-five-number) numbering plan. Central office codes were restricted to the