The little video gives you a better insight. You can see how simple it is and especially how it works. Don't forget that ball at the top. It's not there just to have a nice view. It has an important function in this swing.
A few pictures:

On Flickr: https://www.flickr.com/photos/fotoopa_hs/49942006727

On Flickr: https://www.flickr.com/photos/fotoopa_hs/49941701456

On Flickr: https://www.flickr.com/photos/fotoopa_hs/49941999417
For the real info there is a short video:
https://www.flickr.com/photos/fotoopa_hs/49942010987
I still have a detail picture but I'm going to post it a little later. Most of you will know how it works and why the kids don't stop swinging.
Frans.