DC works well for loading chain and sound files, but I have never seriously considered it for track power.
GHD posted:Interesting! Just curious where you put the 18 volts into the system. I assume to the input side of the TIU . Is this correct?
The TIU variable channels do not pass DC, they're AC only. Using DC through the TIU restricts you to two channels. I believe you could use DC in passive mode using the variable channel, but I've never actually tried it.