You can choose for 540 or 1000 rpm on the chipper. The revs of the flywheel are around 1.000 rpm.
When you want to operate the machine with 540 rpm, the chipper will be equipped with a so called reduction gear. This exists of 2 pulleys with v-belts. In this case you need a cardan shaft with freewheel.
In case you want to work with 1.000 rpm on the tractor, its not necessary to use the reduction gear. Then you need a cardan shaft with freewheel and clutch.