Analog Cameras
Analog or HD cameras operate in a similar way to IP based cameras. The biggest difference is how the signal is moved from camera to the recording device. An Analog camera sends it's signal over a coaxial cable and the signal is then "decoded" at the DVR turning the Analog signal into a digital file for viewing.
Analog and HD cameras often times offer a good value, but most importantly are used to replace current HD and Analog Cameras is order to keep the existing Coaxial infrastructure in place.