... for classroom,meeting room,public security organs, procuratorial organs... E.TRADIO: Clear Speech Microphone,Omni Directional, Monitor Range 10 ... m.*Echo-concelling appearance design, eliminating echo in big hall.*0.8mm pinhole design, clear picking voice.*Restraining high ... Jail, Classroom, Army's department.*According with CE standard. E.TRADIO High-Fidelity,clear speech audio surveillance microphone