cctv
I once had a job where I had to sit in a portacabin, looking at a screen which showed a view of a carpark.

Behind the screen was a window through which I could see exactly the same view from the same angle, as the camera was on top of the portacabin just above the window.

There was one more camera you could flick to, which showed a picture of a wall, as vandals had turned it.

It was a great job.
( FOONLY, Mon 11 Jun 2007, 17:59, archived)