This is a 2 port flap valve allowing proportional control of the exhaust stale air extraction side of the system.
We have chose two exhaust locations Bathroom and a new vent in the living room. This design allows us to have two climate zones one for the living room and one for the bedrooms and the rest of the house.
Its designated Turbo because it has 60 Watt fan embedded in it to boost the air flow to help match the input flow from the inlet and booster fans.