UHPPOTE Non-visual One-to-one Intercom Doorphone linerphone Wired Two-way Audio For 2 Rooms Without Unlock function Intercom doorphone for double rooms The pair units needed to be wired to each other Operation distance 200m/656ft 2-line connected (3.3ft cable come with this parcel) Plug into 110VAC power or insert 4 cells of R6P size AA 1.5V (alkaline) into the cabinet of either one of the talkback pair