A transmission allow extending the number of gears/wheels etc. driven by a given number of physical motors. In this LDD file Jay Kinzie made a wonderful transmission, small and smart, and made only of LDD parts (i.e. parts in the NXT set).

as a side note, there are supposed to be rubberbands on the black ball joints which are on the sliding bits to pull the transmission out of gear. On the medium pulleys that have ball joints on them, they are supposed to be the black peg type, not the grey keyed hole type.

Great work Jay!