Chamberlain PD512 Garage Door Opener, &frac12; HP, Durable Chain Drive Operation, Includes 2-1 Button Remotes, Wall Control Panel Powerful 1/2 hp motor with a rugged and reliable, industrial strength chain drive Accessories include two pre-programmed, 1-button, tri-band frequency remote that provides consistent performance over a long range which includes easy push button wall control and safety sensors Patented security + 2.0 rolling code technology and posilock anti-theft protection assures that once the door closes it stays locked Safety sensors project an invisible beam preventing the garage door from closing on people, pets or other objects Certain vehicle makes/models may require a compatibility bridge device to operate your garage door opener via the home link buttons