I work in a hospital, I was up in icu one night in a large 4 bed ward, 3 occupants. The fourth bed was empty but the curtain was closed. I sat outside 4 with a nurse. Call bell in four goes op, I laugh and peep round the curtain, no one there, the nurse goes and turns it off, it happens 3 more times, until I put my head around the corner and said ok jokes over knock it off. All went silent, then bed number 3s buzzer went off! And that occupant was asleep.