After serious thinking Brian Gaff wrote :
As long as you remember to unlock it before operating it or it might self
destruct!

They do self destruct - there is a deliberate weakened section in the
drive shaft from the motor. Overload the drive and the shaft snaps, as
I found. The attachment on the door in the Crocodile ad., is I think a
wireless obstruction detector. If the door tries to close onto an
object which makes contact with the edge rubber, the door stops and
reverse. I added a IR beam system across my door. If the beam is broken
by an object, 'down' button does nothing, or if it is broken when the
door is going down, it reverses and goes back up. I added a remote LED
indicator to mine, so light comes on when the car is just clear of the
door aperture.