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5.1 Digital Video Recorders (DVR)
Digital video recorders provide a plenty of space to record replay and fast random access of recorded media files. At present age not only separate video recorders available but a lot of live view equipment provide built in option for digital video recording. Concept of digital video recording comes in 1985, later in 1988 Honeywell Inc. got the patent of digital video recorder.[33] This is the first device which is registered as digital video recorder which stored image on hard drive.

This new concept of data storage on hard drives through digital signal became famous very quickly due to its importance of digital video recording on fast and easy access able storage media hard drive. Modern digital video recorders provide more space with fast and random access to the stored date as data is stored on hard drives instead of traditional tape drives. The storage capacity of digital video recorders depends upon the size and number of hard drives installed. The modern systems contain more then one hard drives which provide more data storage capacity according to the required conditions.

There are multiple uses of digital video recorders in the next generation. Digital video recorders are not only used to store CCTV live images but also becoming the part of daily life to record favourite television program which are timed to record for view later by skipping adds to save time. It also provides live storage facility for quick play back or slow motion view.[33]

In digital video recorders image is stored on hard drives which did not allow to deteriorate the quality of image for a long time as compare to tape drive in which the image become fade with the passage of time. In digital video recorders more data is store in less space which saves a lot of space and effort while on tape drives less data is stored on more numbers tape drives, which take a lot of physical space and efforts to store data. There is also no live access of stored data from tape drives which increase the cost of operation with much more effort and time consuming as compare to digital video recorders. 
There are various types of digital video recorders which provide different spaces and stored media options with various functions according to the user’s requirement. which are discussed as follows.

 

5.2 Stand Alone Digital Video Recorders
Stand alone digital video recorders provide full functions of digital video recording functions on a particular location. In these type of video recorders all functions like live imaging storage, backup and play back and other and system operations are manipulate and control in one single location. The storage media in these types of digital video recorders consist of hard drives and digital video disks (DVDs).

These digital video recorders fully support with the Ethernet connectivity which with software applications make enable to manage remotely on WAN. These software applications also provide facility to take live images and manage backup according to the required situation. Digital video recorders provide both normal coaxial and LAN connectivity to CCTV cameras as shown in fig-34