Busy Status Bar

This reminds me of my first job in London looking after the network of a recruitment agency. The consultants got headsets for the first time and one got so annoyed about being interrupted when on a call - because you couldn't tell when people were wearing headsets the whole time - that she taped a big bit of card to the top of her headset saying "ON A CALL" that she could flip up and down depending on whether she was speaking to someone.

I can remember people using various USB "busy lights" since way back in the Skype for Business days. And one of our super old offices has an 80s style wired green/yellow/red light indicator outside of the door, that presumably used to connect to a switch on the desk.

> And one of our super old offices has an 80s style wired green/yellow/red light indicator outside of the door, that presumably used to connect to a switch on the desk.

These light trees used to be (and probably still are in some places) used for the purpose of incident management when in operations centers like NOCs or similar. It is tied to internal status and incident management systems.

That may be but they originated in manufacturing, long before NOCs were a thing.