Two-way Wired Non Visual Intercom Doorbell Office Interphone Intercom System Item is intercom audio door phone, It is powered by AC or DC battery, connected the two unit set by two wires cable ,When you press the doorbell and can talk with other one at another end. Operation distance 200m, 2-line connected, run wiring from point A to point B. Each handset connects to the other, with a new ABS plastic, durable Each phone has a call button. The caller pushes a button that will make the receving handset ring loudly, realize the two-way radio, the sound quality is clear, no noise They are battery powered, even worked in a blackout, and so far, months later with daily use, they are still going strong This is a decent and inexpensive intercom system that uses 8 AA (4 in each handset) and a double wire line screwed onto the back of the bases to connect each settogether, clear communication via, easy to install Suitable for dwelling houses, tier buildings, multiple apartments, offices, factories and so on Please choose to buy the cable spec according to your distance. 50 meters:RVV2*0.5MM 100 meter:RVV2*0.75MM Model Number: TL-109AC/DC * Voltage: DC6V(8x AA battery)(4 in each handset) * Output sensitivity: