The practice of recording CCTV images in digital format is now widely accepted and there are many manufacturers and resellers of what is generically known as the DVR (Digital Video Recorder).
A DVR stores all the images onto internal Hard Drives and presents views of all cameras on a display. All recorded footage can be viewed simultaneously across all the cameras on the system. A user can go back to any time in the recording and playback a recording in a matter of seconds. The recorded images can be stored to hard drives or CDs and archived for as long as necessary.
With the migration to IP based CCTV surveillance camera signals are sent in a digital format, via a network connection. A Network Video Recorder (NVR) will only accept network connected cameras.
As with all technology there are a wide range of products available and it is important to use equipment that will meet the performance required.