2857 Series RTD Threshold Value Switch Wago RTD threshold value switch for RTD sensors, potentiometers and resistors monitors and reports signals of up to two switching thresholds. Providing both digital signal output and relay with normally open contact. Features and Benefits Clipping capability provides analogue signal limitation to output end values Configurable RTD factor Input/output response simulation via configuration display Safe 3 way isolation with 4 kV test voltage per EN 61140