... so on standards. Safety relays are widely used in safety light curtain,safety door,a sudden stop switch and so on safety and sudden loop, ... SR4P2A1B24 are appropriate for E-stop Switch,Safety Gate.The SR4P2A1B24P is appropriate for safety light curtain(PNP).The SR4P2A1B24N is ... curtain(NPN).The SR4P3A1B24 is appropriate for E-stop Switch,Safety Gate.The SR4P2A1B24S is appropriate for two-hands button. ...