AC adaptor

Also called a power supply. All CCTV devices needs power of some sort. Each device has its own power requirements (usually 12 volts with a minimum amperage). The power coming out of the wall (in the US) is 110 to 120 AC. The adaptor converts the AC power to DC power and will adjust it to a specified amperage. The power supply should be included with each item - you usually don't have to buy these separately.