The galvanically isolated safety barriers TSU400 are valid alternative to passive barriers because they don’t need a high integrity I.S. ground, being the isolation between the safe area and the hazardous area guaranteed by a transformer. TSU400 series barriers have an intrinsic voltage regulation of the supply and are designed for connection to ON-OFF sensors having a mA output so that they permit to interface 5/13 mA two wire switching instruments also giving a relay output. They are especially suitable for ships applications and for hazardous areas installations being certified [EEx ia] IIC. Great advantages are offered by the use of TSU400 series barriers interfaced with Valcom® ultrasonic level switches ASL400 series.