The Deer Fence Mighty Mule Dual Driveway Gate Opener is battery powered; the battery charge is maintained by either the AC Transformer (included) or the Solar Panel accessory. The battery acts as its own backup during a loss of power service and will provide power for many opening and closing cycles before needing a recharge. Mighty Mule E-Z Gate Openers feature an auto-close feature that is adjustable from 1-120 seconds, so you don't need to worry if you closed the gate, or you may turn it off and open and close the gate manually using your remote transmitter. It also has an adjustable "obstruction sensing" feature that automatically reverses the gate for 2 seconds and stops when the gate encounters an obstruction. The Mighty Mule E-Z Gate Opener The Mighty Mule E-Z Gate Opener includes: mounting hardware, transformer, transmitter, installation manual and DVD, gate opener arm, control box, receiver, control board and battery. Mighty Mule is a registered trademark of GTO Inc.