all right i came across this in How Stuff Works. the cool thing is that there are no specific ratio it changes how you want it to. its powered by a main motor and then the two servos (A and B) change the position of the two adjustable gears changing from a high to low ratio. note my arrows are slightly off so here's another pic
heres a link that explains more (
http://auto.howstuffworks.com/cvt.htm) this type of transmission is more efficient than your standard gear change transmission. it even was in a couple cars for some time but just never got the publicity needed to make it in most cars. it has a smooth shift and you can have any gear ratio you want.