I have an old rotary dial telephone sitting on top of my PC. Not only does it ring REALLY LOUDLY (because I set it that way) and makes me anxious, I can tell when someone else is on the line!
For example, someone starts dialing a number on another extension, I can hear the clapper in mine click out the numbers. This requires the other extension to also be a dial phone. Also, when someone picks up other extensions (dial or touch tone) I can hear this one go “click!”
If I wanted to I could offencively spy on everything going on around here. (:<