Talking of barriers, the one at Lossie was the source of endless amusement to the inmates of Gordonstoun, who thought it was funny to jump the fence and raise it during the night. The heavies, getting fed up with this, wired the case to the mains. It must have worked, as they were commended on their initiative, but had to un-wire it.
If we were working on the barrier, we would isolate it locally, so nobody at the tower could raise it whilst we were working on it.