CCTV (closed-circuit television) is a TV system in which signals are not publicly distributed but are monitored, primarily for surveillance and security purposes. CCTV relies on strategic placement of cameras, and observation of the camera's input on monitors somewhere.
There are two types of security cameras systems, Analog and IP (sometimes refered to as network cameras). Here is a very basic explanation of how they work and what the major difference is between analog surveillance systems an IP camera systems. ... The cameras are connected to the DVR using transmission cables.
The thing is, security cameras need connection (power supply) whether battery or electricity; any one of those. ... Most CCTV cameras are powered by 12V via a power box or power adaptor. Unless you have a UPS or power backup the cameras and recorder will also be powered off if there is no electricity.