▁of ▁dedicated ▁interface ▁devices , ▁it ▁allows ▁PC s ▁and ▁industrial ▁controllers ▁to ▁communicate . ▁Since ▁it ▁is ▁differential , ▁it ▁res ists ▁elect romagnet ic ▁inter ference ▁from ▁mot ors ▁and ▁w eld ing ▁equipment . ▁ ▁In ▁theatre ▁and ▁performance ▁ven ues , ▁R S - 4 8 5 ▁networks ▁are ▁used ▁to ▁control ▁light ing ▁and ▁other ▁systems ▁using ▁the ▁DM X 5 1 2 ▁protocol . ▁R S - 4 8 5 ▁serves ▁as ▁physical ▁layer ▁for ▁the ▁A ES 3 ▁digital ▁audio ▁inter connect . ▁ ▁R S - 4 8 5 ▁is ▁also ▁used ▁in ▁building ▁autom ation ▁as ▁the ▁simple ▁bus ▁w iring ▁and ▁long ▁cable ▁length ▁is ▁ideal ▁for ▁joining ▁remote ▁devices . ▁It ▁may ▁be ▁used ▁to ▁control ▁video ▁surve ill ance ▁systems ▁or ▁to ▁inter connect ▁security ▁control ▁pan els ▁and ▁devices ▁such ▁as ▁access ▁control ▁card ▁readers . ▁ ▁It ▁is ▁also ▁used ▁in ▁Digital ▁Command ▁Control ▁( D CC ) ▁for ▁model ▁rail ways . ▁The ▁external ▁interface ▁to ▁the ▁D CC ▁command ▁station ▁is ▁often ▁R S - 4 8 5 ▁used ▁by ▁hand - h eld ▁controllers ▁or ▁for ▁cont rolling ▁the ▁layout ▁in ▁a ▁network ed ▁PC ▁environment . ▁ 8 P 8 C ▁mod ular ▁connect ors ▁are ▁used ▁in ▁this ▁case . ▁ ▁Pro tocol s ▁ ▁R S - 4 8 5 ▁does ▁not ▁define ▁a ▁communication ▁protocol ; ▁merely ▁an ▁elect rical ▁interface . ▁Although ▁many ▁applications ▁use ▁R S - 4 8 5