There's a whole history of annunciators for summoning servants.[1] Bells, flags, meter needles, all pre-telephone. [1] https://1889victorianrestoration.blogspo

There's a whole history of annunciators for summoning servants.[1] Bells, flags, meter needles, all pre-telephone. [1] https://1889victorianrestoration.blogspot.com/2011/09/everything-you-ever-wanted-to-know.html https://1889victorianrestoration.blogspot.com/2011/09/everyt...