I have been asked to post photos of the ruota. The one I have posted is not a ruota meant for receiving abandoned baies. It can be found in the Certosa di Trisulta in Frosinone but it will give you the basic idea.
The other photo is of the offical ruota at the Hospital of Santo Spirito in Rome no longer in use today however there is a modern, heated version at one of the hospitals in Rome. Even today there is complete anonymity for mothers of abandoned babies.