I remember my parents having "a party line" - I do not remember how many homes/families were connnected to it. At least 8.
Basically, if it was in use, one could just pick up the phone and listen to what the other people were saying. No 911 back then.
Mom frequently talked "in code" because she assumed there were listeners to every conversation.
I do wonder how "private" anything is - or was - as far as that goes.