Habitation Door Alarm Sensor

[Martin_E]

Those contacts are a reed switch, held by the magnet so one side magnet one side switch, exactly the same as the fridge light on a lot of fridges work, door open light comes on in fridge (I saw an auto electrician fit one of those alarm switches to a fridge, the reed switch part had gone and that’s what he had to hand), open habitation door or windows (assuming window switches fitted) alarm goes off.
They were probably fitted there as it saved running and hiding wire up the door frame.

 

[Hutch]

Those contacts are a reed switch, held by the magnet so one side magnet one side switch, exactly the same as the fridge light on a lot of fridges work, door open light comes on in fridge (I saw an auto electrician fit one of those alarm switches to a fridge, the reed switch part had gone and that’s what he had to hand), open habitation door or windows (assuming window switches fitted) alarm goes off.
They were probably fitted there as it saved running and hiding wire up the door frame.

Agree it would have been better fitted at the top of the door maybe midway. Better aesthetically.