... protecting rear devices*Echo-concelling appearance design, eliminating echo in big hall.*0.8mm pinhole design, clear picking voice.* ... loading protection and lightning proof circuit.*Pre-amplifier, directly drive DVR, VCR, headphone, loudspeaker etc.*Excellent voice experience, widely working ... According with FCC,CE standard. I.TRADIO pinhole,hidden,mini,built-in wall Audio Surveillance Microphone