Power Source Transformer or adaptor ( AC 110V-240V ) Assurance_temperature -40~+ 50oC Max_Wiring Distance Within the distance of 50meters, Diameter ≥0.4mm2 wire for power connection from door station to handset Dimension 352x216x75mm /set for white box Weight about 1.40kgs/set Ring Bell Ding Dong Wiring 4 wires in polarity. Extension One door station supports four indoor phones,including one main indoor phone and three extra indoor phone Door Release function Signal Unlocking Specification Features: 1) Doubledingdongchime 2) 1 door station can connect to 4 handsets at most 3) Power supply: adapter