Ring 3 Connection to Existing Door Chime Wiring

How in the world can this work?

It simply puts the Ring 3 in series with existing door chime wiring. It does not supply AC to the Ring. Like trying to put 2 regular lamps in series.

Alao, someone knowledgable please explain what is meant by the staments of a DC transformer?

Are there any elecxtricians on this site?

Thanks