By 1995, many cities in the United States and Canada had more than one area code, either from dividing a city into different areas (NPA split) or having more than one code for the same area (NPA overlay). The overlay method requires that the area code must be dialed in all cases, even for local calls, while the split plan may permit seven-digit dialing within the same area. The transition to ten-digit dialing typically starts with a permissive dialing phase, which is widely publicized, during which dialing all ten digits is optional. After a period of several months, mandatory dialing begins, when seven-digit dialing is no longer permissible. Atlanta was the first U.S. city to require mandatory ten-digit dialing throughout the metropolitan area, roughly coinciding with the 1996 Summer Olympics held there. Atlanta was used as the test case not only because of its size, but also because it had the world's largest fiber optic network at the time, five times larger than that of New York, and it was home to BellSouth (now part of AT&T), then the Southeastern Regional Bell Operating Company, with AT&T's fiber optics manufacturing facility within the city.