This super high gain Spy Microphone is the smallest microphone in the world. This microphone has a built-in pre-amp.   The preamp features low noise, extremely high gain and auto level adjustment by built-in chipset. This Spy Microphone's voltage requirement is DC12 V.  The cable termination is BNC female.  You may purchase an additional BNC male to RCA male connector to convert the cable termination if your DVR require RCA input.