@nkptomo posted:What is passive mode?
Passive mode is using the TIU to add the DCS signal to the power on the track rather than running the power through the TIU (power input terminal and out the power output terminal).
Since your TIU is known to be prone to burnout when overcurrent passes through it- this is a way to still use the TIU but not pass any current through it and lower the risk of damage.