▁the ▁number ▁of ▁channels ▁that ▁a ▁subscri ber ▁cho oses ▁to ▁pay ▁for ▁in ▁a ▁particular ▁package . ▁Ch annels ▁are ▁usually ▁sold ▁in ▁groups ▁( known ▁as ▁" ti ers "), ▁rather ▁than ▁singular ly ▁( or ▁on ▁an ▁a ▁la ▁carte ▁basis ). ▁Most ▁conventional ▁subscription ▁television ▁services ▁offer ▁a ▁limited ▁basic ▁( or ▁" l if eline ") ▁tier , ▁a ▁minimum ▁base ▁package ▁that ▁includes ▁only ▁broadcast ▁stations ▁within ▁the ▁television ▁market ▁where ▁the ▁service ▁is ▁located , ▁and ▁public , ▁educational , ▁and ▁government ▁access ▁( PE G ) ▁cable ▁channels ; ▁in ▁many ▁smaller ▁mark ets , ▁this ▁tier ▁may ▁offer ▁stations ▁from ▁adjacent ▁mark ets ▁that ▁act ▁as ▁default ▁network ▁affili ates ▁for ▁areas ▁not ▁served ▁by ▁a ▁local ▁affili ate ▁of ▁one ▁or ▁more ▁of ▁the ▁major ▁broadcast ▁networks ; ▁however , ▁since ▁the ▁digital ▁television ▁transition ▁in ▁the ▁late ▁ 2 0 0 0 s , ▁these ▁have ▁been ▁replaced ▁in ▁some ▁cases ▁by ▁digital ▁sub ch annels ▁that ▁have ▁agreed ▁to ▁provide ▁a ▁particular ▁network ' s ▁programming ▁within ▁the ▁local ▁market . ▁ ▁E lev ated ▁programming ▁t iers ▁commonly ▁start ▁with ▁an ▁expanded ▁basic ▁package , ▁offering ▁a ▁selection ▁of ▁subscription ▁channels ▁intended ▁for ▁wide ▁distribution ▁( prim arily ▁those ▁that ▁launched ▁between ▁the ▁ 1 9 7 0 s ▁and ▁the ▁ 1 9 9 0 s ); ▁since ▁the ▁ups pring ▁of ▁digital ▁cable ▁and ▁satellite ▁television ▁during ▁the ▁mid - ▁and ▁late ▁ 1 9 9 0 s