In Black and White, and Other Stories, by Jan Mark
Second paragraph of third story ("Nule"):
'What are they for?' said Libby one morning, after roving round the house and pushing all the buttons in turn. At that moment Martin pushed the button in the front room and the indicator slid up to Parlour, vibrating there while the bell rang. And rang and rang.
I was moved to search this out by a memory of hearing one of the stories, "Who's A Pretty Boy Then?", a chilling tale of haunted budgerigars, on Radio 4 one morning in 1982. It's a collection of nine short stories for older kids (mostly set around school or family), all of them with elements of horror, most (but not all) with reassuring endings. They are all really good; the other one that particularly stands out for me is "Old Money", about a cursed shilling coin. I don't think I had come across Jan Mark otherwise; I see she won the Carnegie Medla twice, for books I haven't read (Thunder and Lightnings and Handles). One of those authors who if you see one of her books in a second-hand shop, it's probably worth getting it for a younger friend or relative who you can then borrow it from. Or you can get this one here.