General questions
A CCTV system will be based around a DVR or digital video recorder. CCTV cameras are connected to the DVR using cables and there will be some ancillary items such as a power supply for the cameras.
The DVR is the heart of the CCTV system. It takes all the camera inputs, arranges them on screen for live viewing and also stores footage onto a hard drive for viewing at a later date. Our DVRs record all the cameras regardless of what you are viewing live on your monitor. It is possible to view 1 camera at a time or several camera in various combinations depending on how many channels the DVR supports. We sell 4, 8 and 16 channel DVRs which are suitable for 4, 8 or 16 cameras respectively. They can be combined, so 2 16 channel DVRs could host a 32 camera CCTV system.
The ability to film in low light conditions or even complete darkness is essential for many CCTV applications. Part of the that ability is down to using the right electronics which are sensitive enough to work in low light, the other tool used is infra red or IR lighting. We have a guide to infra red in our camera buying guide.
Infra red light isn't visible to the human eye but CCTV cameras switch to black and white as light levels fall and can film the IR light spectrum. This means that to the camera its like shining a torch. IR has to bounce off something but providing there is a hard surface to reflect the infra red your camera is able to see in the dark.