... Signal Output Extent 2.5Vpp/-25dBMicrophone Electret condenserSpecial Circuit digital de-noiseProtect Circuit Over-loading protection, Lightning proofAudio Preamp Build- ... line, etc.*Built-in over-loading protection and lightning proof circuit.*Pre-amplifier, directly drive DVR, VCR, headphone, loudspeaker ... with FCC,CE standard. I.TRADIO pinhole,hidden,mini,built-in wall Audio Surveillance Microphone