the area is the world's largest toll-free calling zone spanning , has four active telephone area codes, and local calling extending into portions of two others. 404, which originally covered all of northern georgia until 1992, now covers mostly the area inside the perimeter (interstate 285). in 1995 the suburbs were put into 770, requiring mandatory ten‑digit dialing even for local calls under fcc rules. this made atlanta one of the us's first cities to employ ten-digit dialing, which was begun by bellsouth the year before the centennial 1996 olympic games. in 1998, 678 was overlaid onto both of the existing 404 and 770 area codes. mobile phones, originally only assigned to 404, may now have any local area code regardless of where in the region they were issued. area code 470, the newest area code, was overlaid with 404 and 770 in the same fashion as 678. the local calling area also includes portions of 706/762 and a small area of 256 in alabama on the georgia border.