Summary: On–off controls that switch between two different system states need to clearly communicate to users both the current state and the state the system will move to, should the user press that control.
In a recent WebEx meeting with a client, I panicked thinking that I couldn’t turn my microphone on. I was supposed to give a 6-hour presentation — how was I going to do it if I couldn’t even unmute myself? I kept clicking the crossed-microphone icon, but the microphone stayed crossed whatever I did.
Here’s a screenshot: