His second secondary has the same diameter PVC core, but was wound with ~60 turns of much thinner wire—28AWG bell wire to be exact. This match-up induces 10V on the secondary coil from the 4V ...

Pro tip: The low voltage in a doorbell circuit isn’t dangerous, but you can still get an uncomfortable shock if you touch a live wire. Run a cable to the new chime Choose a location for the new ...