The Generator is the power source of the prison, and allows Cameras, Metal Detectors, and Electric Fences to function. Prisons containing any of these three structures will likely have a Generator as well.
Generator status is indicated by the green/red led and can be shut down temporarily by clicking on it. This will power down the electric structures for a short time until the Generator restarts. Because of this, it is recommended to bypass electric fences close to the Generator. The Generator will produce a large sound when it comes online after 20 in-game minutes.