Interface RealtimeMicrophoneState

The microphone in use. Kept while a switch is under way, until the new one is on. Absent outside a call, on a host without a controller, and when the controller has no microphone open (it stopped, or no device could open).

The microphones the browser lists while the call is connected: what SwitchMicrophone can move to. The call has opened the microphone, so the browser gives their names. Empty outside a call and on a host without a controller.

Why no microphone works: the call lost its microphone (the one in use failed and so did the fallback to the default, or the last one went away), so the agent hears nothing until the user picks one with SwitchMicrophone. Kept while the picked one opens, and gone once a microphone is on. Absent while the microphone works or is being switched, outside a call, and on a host without a controller.