Signs of My Times

I'm not really sure what to say about either of these two objects in my building. The one on the left is from the security panel in the lobby. If anyone can tell me why "audible silence" is not completely nonsensical, I'd like to know. I feel good having a "trouble" indicator though: now I always have a way to know for sure.

I understand the one on the right intellectually — there might be times when you'd need to shut down air circulation in the building — but emotionally it just doesn't ring true. In my head I keep seeing this image of someone running out into the hall screaming "it's too cold!" and hitting the switch. And in the South in summer, that's just crazy.