Area codes 613, 343, and 753

Federal government offices in Hull duplicated their entire allocation of multiple exchanges worth of numbers available in 613 as part of a "dual dialability" scheme.

A tiny unincorporated village (like Odessa, Ontario, with no telephone central office but still listed as a rate centre) usually received multiple 10,000-number blocks.

The "Ottawa–Hull" exchange only covers the area that was the city of Ottawa prior to the 2001 amalgamation, plus the former suburbs of Nepean (central part) and Vanier and small sections of other urban communities.

By 2006, the only remaining unassigned exchange prefixes in the entire 819 region were numbers which could not be assigned to the Quebec side of the Ottawa–Hull area without breaking seven-digit dialling between Hull and Ottawa.

Exchange protection in the National Capital Region was ended, except for the "dual dialability" scheme for government numbers on both sides of the river.

[1] This situation could have been avoided had some 1-613 versions of seven-digit Ottawa-Hull numbers been assigned to areas a safe distance from the National Capital Region years earlier.

Within two years, it became apparent that a new area code was necessary due to the continued number allocation problem – an issue exacerbated by the proliferation of cell phones and pagers.

Local telephone companies did not want the expense and burden of changing existing customers' numbers, which would have required en masse reprogramming of cell phones.

Area code 343, an overlay proposed in 2007,[2] and approved by the Canadian Radio-television and Telecommunications Commission on September 10, 2008,[3] was activated for the region on May 17, 2010,[4] several years earlier than originally anticipated.