▁external ▁information ▁systems . ▁ ▁M AP S ▁can ▁operate ▁at ▁sections ▁of ▁any ▁type ▁and ▁number ▁of ▁tracks . ▁The ▁system ▁can ▁be ▁used ▁at ▁any ▁type ▁of ▁the ▁block ▁system , ▁also ▁on ▁railway ▁sections ▁not ▁equ ipped ▁with ▁systems ▁of ▁the ▁interval ▁control ▁of ▁train ▁movement . ▁ ▁The ▁systems ▁ens ures ▁transmission ▁of ▁the ▁announ cement ▁and ▁control ▁of ▁level - cross ing ▁devices ▁when ▁train ▁approaches ▁M AP S ▁operating ▁area ▁on ▁any ▁of ▁the ▁monitor ed ▁tracks ▁ir res pective ▁of ▁their ▁type ▁and ▁block ▁system ▁operation . ▁ ▁Sign al ▁is ▁released ▁and ▁the ▁level ▁crossing ▁is ▁opened ▁only ▁if ▁trail ▁end ▁of ▁train ▁leaves ▁the ▁level ▁crossing ▁and ▁all ▁tracks ▁of ▁the ▁adjacent ▁sections ▁are ▁vac ant . ▁ ▁M AP S ▁ens ures ▁round - the - clock ▁operation . ▁ ▁M AP S ▁oper ates ▁in ▁accord ance ▁with ▁the ▁requirements ▁of ▁technical ▁a est het ics ▁and ▁erg onom ics . ▁ ▁MP B ▁ ▁Computer - based ▁Sem i - Autom atic ▁Block ▁System ▁MP B ▁is ▁designed ▁to ▁substitute ▁out dated ▁relay ▁semi - autom atic ▁block ▁systems ▁on ▁low - int ens ity ▁traffic ▁sections . ▁MP B ▁is ▁used ▁for ▁equipment ▁of ▁new ▁sections ▁as ▁well ▁as ▁for ▁re h abil itation ▁and ▁upgrad ing ▁of ▁existing ▁sem ia ut om atic ▁block ▁systems . ▁ ▁In ▁contrast ▁to ▁its ▁relay ▁analog ues ▁MP B ▁is ▁capable ▁to ▁transmit ▁block ▁signals ▁not ▁only ▁through ▁physical ▁connection ▁lines ▁but