... .m monitoring range, water proof design, can connect directly to DVR, VCR, active loudspeaker, headphone, soundcard of PC and anywhere ... noise, low echo.Pinhole design,covert installation.3.Head and seat are separately, head is as big as thumb.4.Built-in ... protection and lightning proof circuit.12.Pre-amplifier, directly drive DVR, VCR, headphone, loudspeaker etc.13.Excellent voice experience, widely ...