CCTV (Closed Circuit Television) is a surveillance camera. The CCTV is the best way to keep areas under control without the need of sending a guard around. Indoor areas without guards will be overlapped with the Fog of War and the player will not see what's going on in the area. The CCTV will add a moving cone of sight to the area where it is placed.
The CCTV has to be unlocked within the Bureaucracy screen and it needs a CCTV Monitor for it to work. Connect a wire from the CCTV Monitor to the CCTV. If a connection is made from the CCTV to for instance a Status Light, it will output a high signal when it is active.
The CCTV camera needs 3 tiles to move from side to side in order to exercise its full range. For example, if you place a CCTV camera in a corner, it will only move 90° instead of the normal 180°. Rotation is important and it is a bit tough to see the actual rotation during placement. If your camera doesn't work, check if it's simply pointing towards the wall. If so, dismantle it and try again.
CCTV cameras provide a visual assistance for the player only. Guards do not utilize it (e.g. if a camera spots some prisoners fighting, no guards will be called by automatically). If the Fog of War option is not used, CCTV does not have any benefit for the game, but can still be utilized to earn money from a grant. Deploying guards in all rooms that are to be watched is more expensive, but has the effect of removing fog of war and having guards available for intervention both at once.
As there is no Fog of War outside of buildings, CCTV cameras don't have any effect outdoors.