As humans are highly adaptable, Deaf people are quite innovative with communication across all those centuries.
In the olden days, hearing people knocked on the doors of one's home. Deaf people used a flashlight hanging outside the door. When a visitor came to the door at night, s/he waved the flashlight through the window.
Or, they'd wave hands in front of the windows. If one has a dog, it'd bark, notifying the owner.
Radio Shack flash ringers were commonly used among early videophone users as well as TTYs in other rooms in the 1990s.
Every dorm room on the campus of Gallaudet University has a doorbell (light switch) outside the dorm room that would flash light inside.
When my parents bought a land to build a brand new house in the 1990s, they instructed the builder to design and wire that every room has two different sockets: one for regular electrical things and another for plug-in bulbs or lamps that will flash when a phone or doorbell rings. To this day as of this writing (2015), they are still living in the same house.
At a conference hotel, one would knock on the door really hard or wave a paper under the door unless one has a mobile number to text the other.
Not unlike hearing people, Deaf people text from outside these days.