Yukon: 12/12 comes under the heading of RTFB! The newer A/G seven holes models already have all the bells and whistles built in to do everything you want to grow our favorite herb, including the light schedules. Just make sure you have one of the newer seven holes models or an upgraded "Classic." Don't use their nutes or waste your money trying to grow ganja in the A/G-3 or the "Space saver 6." Do add an air stone, an aquarium air pump, an air line and a one way check valve to oxygenate the nutes in your reservoir.
If you have an older, shorter, "Calssic," model, at their website, they offer an upgrade kit with a taller 24" arm/light stand, a hood with three high intensity CFL's, instead of two, and a longer figure eight cord.
They also sell a figure eight cord separately for around $10 and a remote timer for 12/12 lighting but theirs is real expensive. The timer and figure 8 cord is for those of us who have the older "Classic" models, but you can get those accessories a lot cheaper else where. Radio Shack has the figure eight cord for around $7. The 99cents store has them for, you guessed it, 99 cents. Same cord, same wattage rating only about a foot shooter and so far that hasn't mattered.
You can get the remote light timer, like the one people use for their Christmas lights, from Harbor Freight Tools for about $5. Just about everybody has them at a higher price. The newer models already have the three lamp hood, the taller arm/light stand, the longer figure eight cord and the timed light schedules pre-programmed into the unit. They not only have a 12/12 cycle but a 24 hours on cycle if you really want to push your plants. They have all of this information at their web site. I hope that helps. HSA