S - 2 3 2 ▁are ▁available ▁to ▁allow ▁a ▁personal ▁computer ▁to ▁communicate ▁with ▁remote ▁devices . ▁By ▁using ▁repe aters ▁very ▁large ▁R S - 4 8 5 ▁networks ▁can ▁be ▁formed . ▁T SB - 8 9 A , ▁Application ▁Gu idel ines ▁for ▁T IA / E IA - 4 8 5 - A ▁does ▁not ▁recommend ▁using ▁star ▁topology . ▁ ▁App lications ▁ ▁R S - 4 8 5 ▁signals ▁are ▁used ▁in ▁a ▁wide ▁range ▁of ▁computer ▁and ▁autom ation ▁systems . ▁ ▁In ▁a ▁computer ▁system , ▁SC SI - 2 ▁and ▁SC SI - 3 ▁may ▁use ▁this ▁specification ▁to ▁implement ▁the ▁physical ▁layer ▁for ▁data ▁transmission ▁between ▁a ▁controller ▁and ▁a ▁disk ▁drive . ▁R S - 4 8 5 ▁is ▁used ▁for ▁low - speed ▁data ▁communic ations ▁in ▁commercial ▁aircraft ▁cab ins ' ▁vehicle ▁bus . ▁It ▁requires ▁minimal ▁w iring , ▁and ▁can ▁share ▁the ▁w iring ▁among ▁several ▁seats , ▁reducing ▁weight . ▁ ▁These ▁are ▁used ▁in ▁program m able ▁logic ▁controllers ▁and ▁on ▁factory ▁flo ors . ▁ ▁R S - 4 8 5 ▁is ▁used ▁as ▁the ▁physical ▁layer ▁underlying ▁many ▁standard ▁and ▁propriet ary ▁autom ation ▁protocol s ▁used ▁to ▁implement ▁industrial ▁control ▁systems , ▁including ▁the ▁most ▁common ▁versions ▁of ▁Mod bus ▁and ▁Prof ibus . ▁ ▁is ▁a ▁propriet ary ▁communic ations ▁protocol ▁used ▁by ▁Allen - B rad ley ▁in ▁their ▁line ▁of ▁industrial ▁control ▁units . ▁ ▁Util izing ▁a ▁series