▁x xxx , ▁ 7 1 xx ▁x xxx , ▁ 8 0 xx ▁x xxx ▁and ▁ 8 1 xx ▁x xxx ▁numbers ▁became ▁available ▁for ▁general ▁use . ▁These ▁began ▁to ▁be ▁allocated ▁anywhere ▁in ▁London , ▁with ▁no ▁regard ▁for ▁the ▁ 1 9 9 0 - 2 0 0 0 ▁inner / outer ▁London ▁ge ographical ▁split . ▁ ▁In ▁all ▁of ▁the ▁other ▁areas , ▁new ▁BC 0 x ▁x xxx ▁and ▁BC 1 x ▁x xxx ▁numbers ▁became ▁available ▁for ▁general ▁use ▁at ▁the ▁same ▁time ▁( where ▁' BC ' ▁stands ▁for ▁' 7 6 ' ▁in ▁Cov entry , ▁' 2 0 ' ▁in ▁Card iff , ▁etc .). ▁ ▁Northern ▁Ireland ▁▁ ▁In ▁Northern ▁Ireland , ▁the ▁situation ▁was ▁more ▁complicated . ▁While ▁the ▁primary ▁reason ▁for ▁the ▁changes ▁was ▁the ▁lack ▁of ▁number ing ▁capacity ▁in ▁B elf ast ▁( 0 1 2 3 2 ), ▁this ▁was ▁not ▁the ▁only ▁reason . ▁When ▁ST D ▁codes ▁were ▁introduced ▁in ▁the ▁ 1 9 5 0 s , ▁Northern ▁Ireland ▁was ▁allocated ▁only ▁ 1 4 ▁area ▁codes ▁for ▁ 3 4 ▁charg ing ▁groups . ▁Normal ▁practice ▁in ▁Great ▁Britain ▁was ▁to ▁allocate ▁one ▁area ▁code ▁per ▁charg ing ▁group ▁but , ▁as ▁calls ▁to ▁Northern ▁Ireland ▁were ▁national ▁rate ▁from ▁anywhere ▁in ▁GB , ▁it ▁was ▁not ▁seen ▁to ▁be ▁necessary ▁to ▁differenti ate ▁between ▁all ▁of ▁them . ▁So , ▁area ▁codes ▁covering ▁multiple ▁charge ▁groups ▁(" m ixed "