There are several different types of CCTV (Closed Circuit TeleVision) power supplies.  Currently in the digital video security industry there are two basic types of power that are used; 1.) 24  Vac and 2.) 12 v DC.  Most digital video cameras utilize a low-voltage power supply so there are not as many potentially dangerous factors to be concerned about as there is if they used full household Alternating Current (AC).