The power supply unit is the piece of hardware that's used to convert the power provided from the outlet into usable power for the many parts inside a CCTV Camera or electronic equipment. The power supply unit is often abbreviated as PSU and is also known as a power pack or power converter.
It converts the alternating current (AC) into a continuous form of power that the electronic components need in order to run normally, called direct current (DC). It also regulates power surges and overheating by controlling voltage, which may change automatically or manually depending on the power supply.
Motherboards, cases, and power supplies all come in different sizes called form factors. All three must be compatible to work properly together. The side of the PSU facing outside the case has a male, three-pronged port that a power cable, connected to a power source, plugs into. There is also often a power switch and a power supply voltage switch.
Power supply units are rated by wattage to show how much power they can provide to the electronic equipment. Since each equipment part requires a certain amount of power to function properly, it's important to have a PSU that can provide the right amount. A PSU is not usually user serviceable. For your safety, it's usually wise to never open a power supply unit.