Gearbox with a drive sprocket on the input shaft and a timing belt pulley on the output shaft. Transmission assembly takes Stairclimber step pedal movement input and outputs to alternator.

NOTE: The timing style pulley is no longer available from the original equipment manufacturer. Pulley can be upgraded to the quieter, Poly-V design.
To make the upgrade, it is necessary to replace the belt and alternator pulley when replacing the transmission pulley.