The indoor unit is powered by the outdoor unit and should a power outage occur, the system is automatically restored when power returns. Ductless systems allow for flexibility. A single-zone (also called a mini-split) ductless system allows you to control the temperature of one room by connecting an outdoor unit to an indoor unit, with no ductwork needed. An outdoor mini-split unit is placed outside your home and is connected to an indoor mini-split unit by small cables and a refrigerant line through a hole in the wall.