A DVR is a digital video recorder. These essentially take the video from the digital or analogue cameras that you have placed in or around your property and record it into a digital format onto a hard drive. DVRs can record very high quality video for weeks or even months on end with very little maintenance. They work by means of a video capture card that is housed within them which is a graphics card which captures the signal from the cameras and then stores the video on the hard drive.
As to how long a DVR can record footage for is dependent upon a number of factors including the amount of available hard disk space, the number of cameras in the system and the frames per second (FPS) being used. The length of footage recorded can be extended by various means including the use of motion detection which only records when there is movement in front of the cameras.
