Talkback
Talkback is applied to the mix when an audio channel that is set to talkback is manually triggered. Talkback is often used in a studio for internal communications, the background mix is ducked when the talkback button is pressed so that talent can hear the director over the background. Setting for talkback are similar to ducking except there is no threshold or depth.
When talkback is active for a channel the Mute button is replaced with Talkback. When the Talkback button is off, the channel is muted and talkback is not applied. When the Talkback button is held, the channel is unmuted and the mix will be attenuated for as long as the button is held.