1.Made from aluminium alloy even master adopt specialized speaker also with 37cm metallic flexible hose MIC,easy talk with the substation; 2.Round design and small size.used the four-corn high steady and full shielding aluminium foil wire,strong anti-interference can work with metal material.(option:metal shell or plastic substation); 3.Volume is nature,clearly,can be adjusted by separately; 4.Inside circuit board pass the microcomputer dispose,can lock the volume track each other and avoid noise; 5.have recorder jack can output the voice from master and substation also work with others monitor equipment; 6 can have (hello,welcome,please check your money,wish to service you again)Apply:Bank,Hospital,Station,Dock,Ticket station etc.