>I was back at that hospital for other business a little while ago, and
>they've renovated the lobby. That phone (or... whatever it was?) is
>no longer there. That makes me sad, partly because the photo I got of
>it was a bit crap. Which will tend to happen when you're taking
>photographs while having an attack of severe ataxia. :/

At a guess, I'd say this was a really old intercom system. The reason for the sign was so people wouldn't try to dial an outside line, and waste everyone's time when it doesn't work.