Recirculating gearboxes are used in many areas of mechanical engineering. The author of this work attributes the various designs to a general basic form by means of uniform designations and indexing. This results in generally valid and easily programmable calculation equations for all designs. These are summarized on three clearly arranged worksheets, greatly simplifying the design and construction of the gearboxes. The book contains more than 150 illustrations with design examples. From the contents: - History of recirculating gear units. - Marking of the recirculating gearboxes. - Basic laws of recirculating gear units. - Applications of simple planetary gears. - Composite recirculating gearboxes. - Constructive notes. - Summary of the notes. - Worksheets. - Literature, names, and expert indexes.