2 4 0 0 ▁bits ▁per ▁second ▁is ▁called ▁frequency ▁shift ▁key ing ▁( FS K ). ▁ ▁Two ▁radio ▁frequencies ▁represent ▁binary ▁ 0 ▁and ▁ 1 . ▁ ▁Radio ▁transmission ▁such ▁as ▁F SK ▁sends ▁data ▁digit ally . ▁ ▁Until ▁recently ▁radio ▁transmission ▁was ▁subject ▁to ▁short ▁range ▁and ▁inter ference ▁by ▁other ▁radio ▁sources . ▁ ▁A ▁fairly ▁recent ▁technology ▁called ▁spread ▁spectrum ▁perm its ▁much ▁more ▁robust ▁radio ▁control ▁of ▁score boards . ▁ ▁Sp read ▁spectrum , ▁like ▁the ▁name ▁implies , ▁dist ributes ▁the ▁signal ▁over ▁a ▁wide ▁portion ▁of ▁the ▁radio ▁spectrum . ▁ ▁This ▁helps ▁the ▁signal ▁resist ▁inter ference ▁which ▁is ▁usually ▁conf ined ▁to ▁a ▁narrow ▁frequency ▁band . ▁ ▁Sc ore boards ▁in ▁various ▁sports ▁ ▁North ▁American ▁football ▁ ▁In ▁both ▁the ▁United ▁States ▁and ▁Canadian ▁football ▁codes , ▁the ▁minimum ▁details ▁displayed ▁are ▁the ▁time ▁and ▁score ▁of ▁both ▁teams . ▁ ▁A ▁typical ▁high ▁school ▁ ▁score board ▁will ▁addition ally ▁ ▁display ▁the ▁down , ▁the ▁yard age ▁of ▁the ▁line ▁of ▁sc rim m age , ▁the ▁yards ▁to ▁go ▁until ▁a ▁first ▁down , ▁the ▁team ▁with ▁the ▁possession ▁( us ually ▁sign ified ▁with ▁the ▁outline ▁of ▁a ▁football ▁in ▁lights ▁next ▁to ▁the ▁possess ing ▁team ' s ▁score ) ▁and ▁the ▁quarter . ▁ ▁High er ▁levels ▁will ▁also ▁include ▁play ▁clock s ▁and ▁the ▁number ▁of ▁time ▁out s ▁left ▁for ▁each ▁team . ▁ ▁American ▁football ▁score boards ▁may ▁include