Best voltage to power TIU

You can use the 15 volt setting, but......? What is the ouput current/wattage capability of the unit??

I use 16V(nominal) from a wall wart normally used for home security systems-- has a 1.3 Amp capacity. I know the MTH manual says 12-24VAC and 1 amp minimum, but if you aren't powering AIU's, then the TIU draws about .5A. I'd go with the 1 amp min. to be safe for the future when you add AIU's---

I use 18v that way it works for both DCS and TMCC, the later doesn't like anything higher than 18v.

Southern Mike,
This really depends on how well you engineered your DCS layout and if as K-man says you are also running TMCC. However for a correctly set up DCS only
layout, I have found you can run a minimum of 16V, and still have 9-10 DCS signal. I am much like K-Man however my power is set at 18V all the time even though I am running strictly a DCS layout. I engineered in this manner from the start.
PCRR/Dave