Descriptions: 1. Suitable for the Bank,Securities Company,Hospital,Station ect.where the Burglar-proof glazing is installed. 2. The main unit has aluminum alloy shell,and the extension has built-in speaker, This system has simple connection for DIY operation 3. This system has top-quality speaker and high-sensitive microphone.Especially the metal tube microphone is deal for the counter and the dual-way intercommunication. 4. The voice from the system is clear and natural There is a swith only for the volume control. 5. For this system. We adopted the advanced microcomputer from USA Track-interlock technique ensures the stable performance without noise and side-tone. Parameters: All of our items are Brand New This item is suitable for short distance communication. It is simple, economical and convenient. Voltage:100~240V Working voltage:DC9V Most working current:600mA Main sound box,sub-sound box:2w-2w 100Hz-15KHz Inside microphone:-48db±2db 20Hz-20KHz Outside microphone:-48db±2db 20Hz-16KHz Frequency response:100Hz-12KHz Destop unit dimensions:182*120*56(mm) Wall mount unit dimensions:61*85*24(mm) The speaker cord is 191cm Package Included: 2 x Host (inside) 2 x Vice machine (outside) 2 x AC Adapter Note: If you need more, please feel free to contact us, we will give you the best discount.