I had never seen such small ferries, so I'm posting these photos purely for informational purposes for anyone who is as interested in them as my wife and I were when we came upon them.
The first photo displays how the system works in the first two ferries. The boat is attached to a guide cable and another cable is pulled by hand by someone standing in the boat. (The first photo was captured by my wife and post-processed by me.)
The man who runs the second ferry is about to lose his business because a small pedestrian bridge is being built across the river. Even though this tiny ferry is at the end of a road as opposed to the side of the road as in the case of the first ferry, I was really surprised that it is included in our GPS device's map.
We used the third ferry to cross in our car both ways. It's difficult if not impossible to tell from the photo that the ferry is pulled by a man-powered wench. That must be really difficult when it is fully loaded with four cars and all of the people riding in them.