Talk:Feature group

Feature Group D not described correctly

When Feature Group D began, callers were instructed to dial 10 then the three-digit code for a carrier (e.g. 288 for AT&T, 333 for MCI, etc.). As the supply of three-digit codes appeared destined to exhaust, the industry promoted replacing 10 with 1010, and after a long permissive period, 1010 became mandatory. Once it was mandatory, the last zero migrated to the beginning of the three-digit carrier codes, making them four-digit and allowing new codes that did not begin with a zero, and changing the access from 1010 to 101. A breeze through the list of assigned codes shows all digits 0 to 9 are in use as the initial digit of four-digit codes, leaving no apparent room for expansion to five-digit codes should it be necessary in the future. GBC (talk) 01:16, 1 February 2026 (UTC)