I think it's different at different locations. Some it's just a buzzer, but others it's like an intercom. Were it the latter, I expect someone would have said something on the other end.

[ She takes a seat against the opposite wall, not looking too bothered just yet. If they're stuck more than a hour, then she'll start feeling annoyed. ]

I'm Angela. What's your name?

[ The cat seems young to her, but she can't really tell. Do they live cat lives or human lives when it comes to years? ]