Abus opening detectors 24 core white 2m4m5m abus mk2000w the abus mk2000w opening detector 2 core white 5m is a magnetic contact for protecting doors and windows an unauthorised opening is detected and reported to the alarm panel 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 minimum distance of 13mm apart the electric circuit of this no opening detector is normally open no if the