Definition
A DVR is the recorder analogue cameras connect to over coaxial cable; it digitises the picture inside the unit. An NVR is the recorder IP cameras connect to over network cable; the picture is compressed in the camera and arrives over the network. For new installations NVR plus IP cameras is the standard: higher resolution, one cable with PoE, network access to each camera. Where analogue cabling exists, a DVR or hybrid unit can continue to be used. Recording time depends on disk capacity, camera count, resolution and motion detection; disks should be surveillance-grade and the recorder on a UPS. Remote viewing should use a secure connection, not direct exposure of the unit to the internet.
How SMB Teknoloji uses it
In camera projects we size the recorder by camera count and required retention days, separate the camera network with a VLAN and set up phone viewing over a secure connection.