Most CCTV cameras do not have their own power source or battery backup. They are powered by a DC (direct current) source supplied by a cental power supply (AC/DC) unit. The AC power supply is powered from the mains power supply and will simply cut-out if there is a power outage. By plugging the AC power supply into a suitable uninterruptible power supply, along with any associated security equipment such as an DVR/NVR camera recording system, a CCTV system can be kept running during a power outage, mains power failure or abnormal mains power event.