Surveillance DVR’s, or digital video recorders, enable recording and storage of lots of surveillance video. Most have disks storing of anywhere from one half to 4 Terabytes for video surveillance systems. Video surveillance DVR's can be set to motion-triggered recording, saving greatly on storage. Motion-triggered alerts can be set up via text and / or email, some with picture attached. Add-on video surveillance cameras can also be found in the next category at the left.