Pinhole Style Microphone,Omni Directional, Monitor Range 10-30sq.m,suit for prison,jail room,small room,very secretly Pinhole Style Microphone,Omni Directional, Monitor Range 10-30sq.m,Size 60mm*22mm, Weight 30g, White / Black CasePart of customers: Guizhou Provice prison; Dalian city jail rooms etcDetail Introduction:*Professional wired audio surveillance & monitoring microphone.*Low noise, Low ...