transit sliding door switch?

[gasgeezer]

I have a ford transit and have just noticed what appears to be a broken switch on the frame where the sliding door touches {not the contact switch at the front of the door} it is on the right hand side of the opening can any one tell me what it is for?

 

[Burnerman]

Something tells me its to do with the alarm system, but do check things like the internal lamps (especially if there's been a step at the side door) and the central locking, just to see if all is well there.
John