The SP-S1 is a single channel coaxial video surge protector used in CCTV applications to protect surveillance DVRs, multiplexers, and any other type of video equipment from power surges.  Two of these surge protectors should be used per camera, one on the security camera end and one on the surveillance DVR end to fully protect your DVR.  This unit can also used in conjunction with the SP-R16 16 channel video surge protector.