"E" is Eastern Time Zone, "C" is Central Time Zone, "M" is Mountain Time Zone, and "P" is Pacific Time Zone. Occasionally, an area code will fall in more than one time zone. In this case, the abbreviation is a combination of the previous abbreviations. Some area codes are shown with time zones referencing Universal Coordinated Time (UTC).
Additional technical status can be retrived from the North American Numbering Plan Administration on the 762 area code specific link here.
TELEPORT COMMUNICATIONS ATLANTA, INC. - GA, BELLSOUTH TELECOMM INC DBA SOUTHERN BELL TEL & TEL, VERIZON WIRELESS OF THE EAST, LP - GA, POWERTEL ATLANTA LICENSES, INC., NEW CINGULAR WIRELESS PCS, LLC - GA