... for classroom,meeting room,public security organs, procuratorial organs... E.TRADIO: Clear Speech Microphone,Omni Directional, Monitor Range 10 ... loading protection, Lightning proofAudio Preamp Build-inOutput connector Power+, Audio and Public GND Cable 3 x 0.5mm2 RVVP ... , Jail, Classroom, Army's department.*According with CE standard. E.TRADIO High-Fidelity,clear speech audio surveillance microphone