For some inexplicable reason Dell has chosen to mark the button as "mute mic" (mic icon + X). So if the LED on the keyboard is lit up, the microphone is off, or

For some inexplicable reason Dell has chosen to mark the button as "mute mic" (mic icon + X). So if the LED on the keyboard is lit up, the microphone is off, or rather, the microphone muting is on on. Brilliant design.