DAB tuner: Function
WARNING: This page is about a different car, the 2013 BMW X5, 2012 BMW X5, and 2011 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
The vacuum unit is connected to the vacuum supply via the pressure converter. The applies a variable vacuum to the vacuum unit according to the commands received from the DDE control module. The DDE control module controls the pressure converter by means of a square-wave signal with a duty factor (= variable pulse width) between 50 % and 75 %.