As standard the units are supplied with the shaft 1 or sometimes referred to as A as the input. It is also the shaft, which is housed, in an extended housing on ratios above 1.5:1 on the range N. When using a 1:1 ratio gearbox it does not matter which shaft is used as the input as the speed will remain constant. However it is important to ensure that the correct shaft is used on higher ratios other wise the unit will end up increasing the speed.