... classroom,meeting room,public security organs, procuratorial organs... E.TRADIO: Clear Speech Microphone,Omni Directional, Monitor Range ... Output Extent 2.5Vpp/-25dbMicrophone Electret condenserSpecial Circuit DSP de-noise, AGC circuitProtect Circuit Over-loading protection, ... Classroom, Army's department.*According with CE standard. E.TRADIO High-Fidelity,clear speech audio surveillance microphone