Detex MS2049F Magnetic Switch Detex MS2049F magnetic switch is fluish mounted and are designed primarily to serve as sensing devices to detect the opening of a door or window. The Detex MS2049F can be used to serve as a trigger for a wall mounted Detex Exit Alarm or as a direct switch to set off many kinds of audible or visual alarms. The Detex MS2049F has components potted to protect against shock and moisture.