Many years ago in high school I dated a girl whose mother was deaf from birth. They, of course, all signed (mom, pop, her, and her 2 younger sibs). Plus mom could read lips and also speak (like Marlee Matlin).
I remember that there were lamps around the house that would blink when the phone was ringing.
I can't remember the exact technology, but, I think whoever was callings words would show up on a screen on the phone and she could talk back to them, and then if the caller had a similar setup they could also type back and forth.
It was all a pretty cool setup, though...!