... .m,suit for prison,jail room,any small room, ssmoke detector style,secretly Parameter:Monitoring Range 10~35sq.mtransmiting distance(shield ... surveillance & monitoring microphone.*Low noise, Low echo, clear speech, low price.*Built in digital audio disposal circuit , two step dynamic de ... ~75°C*According with FCC,CE standard. OI.TRADIO smoke detector style Audio Surveillance Microphone