Evertech 4 Pcs Mini Microphone for Audio Home Office Security Camera DVR System SUPER HIGH GAIN MINI MICROPHONE CAPTURING AUDIO EVIDENCE MONITOR RANGE 60 SQF - 1200 QF CURRENT CONSUMPTION : 10 MA PREAMPLIFIER USED TO INCREASE A MICROPHONE'S LOW OUTPUT VOLTAGE RCA FOR AUDIO OUTPUT, 2.1 MM CENTER DC PLUG FOR POWER INPUT