There are two kinds of surveillance systems: analog and digital.
Traditional analog systems record the signal directly from the camera. Cameras that use this technology are rated withTV lines (TVL). They record with a Digital Video Recorder (DVR).
The signal from the camera is converted into numbers and then saved. Cameras that use this technology are rated with a number followed by the letter "p," such as 720p. This kind of system will use a Network Video Recorder (NVR).
For the most part, Zmodo digital cameras will not work with an analog DVR and vice versa.