Was this the harmonic drive that got Bonner into patent infringement? It is more commonly used today in industrial robot systems. Here is a site that explains the basic concept for anybody that haven’t seen the technology. Harmonic drive offers zero backlash and a high numerical reduction with very few components.

http://www.britannica.com/eb/art-61260?articleTypeId=1

Note that the flexspine has fewer teeth than the rigid spine. It takes the wave generator rotating many times to get one rotation of the flexspine, thus giving the speed reduction