▁any ▁need ▁to ▁change ▁them , ▁although ▁it ▁did ▁require ▁some ▁care ▁by ▁the ▁user ▁and ▁could ▁be ▁restrict ive ▁in ▁the ▁content ▁of ▁the ▁bar codes ▁that ▁could ▁be ▁handled . ▁ ▁USB ▁ ▁Later ▁bar code ▁readers ▁began ▁to ▁use ▁USB ▁connect ors ▁rather ▁than ▁the ▁keyboard ▁port , ▁as ▁this ▁became ▁a ▁more ▁convenient ▁hardware ▁option . ▁To ▁retain ▁the ▁easy ▁integration ▁with ▁existing ▁programs , ▁a ▁device ▁driver ▁called ▁a ▁" software ▁w edge " ▁could ▁be ▁used , ▁to ▁em ulate ▁the ▁keyboard - imp erson ating ▁behavior ▁of ▁the ▁old ▁" key board ▁w edge " ▁hardware . ▁ ▁In ▁many ▁cases , ▁a ▁choice ▁of ▁USB ▁interface ▁types ▁( H ID , ▁CD C ) ▁are ▁provided . ▁Some ▁have ▁Power ed U SB . ▁ ▁W ire less ▁networking ▁ ▁Some ▁modern ▁hand h eld ▁bar code ▁readers ▁can ▁be ▁operated ▁in ▁wireless ▁networks ▁according ▁to ▁IE EE ▁ 8 0 2 . 1 1 g ▁( W L AN ) ▁or ▁IE EE ▁ 8 0 2 . 1 5 . 1 ▁( B lu et ooth ). ▁Some ▁bar code ▁readers ▁also ▁support ▁radio ▁frequencies ▁viz . ▁ 4 3 3   M Hz ▁or ▁ 9 1 0   M Hz . ▁Read ers ▁without ▁external ▁power ▁sources ▁require ▁their ▁batter ies ▁be ▁re charg ed ▁occasionally , ▁which ▁may ▁make ▁them ▁un su itable ▁for ▁some ▁uses . ▁ ▁Resol ution ▁ ▁The ▁sc anner ▁resolution ▁is ▁measured ▁by ▁the ▁size