FYI, they have battery powered ones with an indoor chime.
Got a rechargeable one with a recording peep hole (apparently no one can figure out what the button with the little bell on it does)...
Put a sticky note on the door with an arrow pointing to the button with the bell on it and prominently labeled it "DOOR BELL" (that worked for nearly 50% of the people); eventually the sticky note will fall off; hopefully, by then most people will have figured it out...
..Then I installed the Door knocker.
Enjoy!
