Abus opening detectors 24 core white 2m4m5m abus mk1010w the abus mk1010w opening detector 4 core white 4m is a magnetic contact for protecting doors and windows any unauthorised opening is detected and reported to the alarm center the opening detector consists of a magnetic contact reed and a magnet which are fitted parallel in front of or at right angles to each other at a distance of 13 to 25mm apart the electric circuit of this nc opening detector is normally closed nc if t