Whiteout mode prevents all injected audio from being played on the stream. Instead, your terrestrial audio will be played. Setting up whiteouts will require some effort on the part of your engineers / traffic supervisors, but once set up it provides a lot of flexibility and does not require access to the streaming computer.
The station engineer, or whoever handles the AMS, creates two new carts from a promo / station liner / PSA with modified titles. Place these carts in the AMS category normally defined for these types of audio. Set one cart's title to START WHITEOUT, and the other to END WHITEOUT.
To begin a whiteout, play the START WHITEOUT cart in the stream. To end it, play the END WHITEOUT cart.