RS Pro Compact Reed Proximity Sensors. RS Pro compact reed proximity sensors feature normally open contacts that close in the presence of a ferrous metal. Features and Benefits. Normally open contact. 6 mm activation distance (may vary depending on iron content). Switching voltage 140 V ac, 200 V dc. Maximum switching load 10 W, 0.25 A. Operating temperature -40° to 85°C. ABS housing material. 2 core cable