During one of our meetings, member Curt McKitrick presented this article that he obtained from the internet (see link below). It may help those of us who use the DT400 on our layouts and during the shows:

Fellow Digitrax DT400 Radio RF users,

Ever lost control of your entire layout for a short duration? I'm talking about all the radio throttles in the room. I have found the cure. This is directed at users of the DT 400 throttle running tetherless on radio, not IR mode. I have only followed thru regarding RF use.

The fix:
Disable the Power Save mode by using Option #2 on the DT400. I set mine at Hex X87. On the keypad, hit "Option"," Enter" consecutive times until Opt #2 shows, and dial in the Hex value with the right dial. Hit "Enter" .Continue hitting "Enter" until it rolls out of options mode. Page 108 in the Digitrax Manual.

The story behind it all:
The DT 400 has a power save mode where the throttle goes into a hibernation state (noticeably the display says "r-PS"), and only comes back by making some kind of adjustment to the throttle, like a speed change. I never thought much of it since the throttle jumped right out of this power save mode, and I had minimal trouble regaining control of my train. The issue goes much deeper than just a simple power save state.

I run six throttles on the layout. Every 20 minutes or so all tetherless operators would experience total loss of throttle control and runaway trains were the order. It wasn't until we hooked up a digital 900mhz radio with a signal strength meter and a high gain antenna, that I was able to start tracking down the cause. A full strength carrier is broadcast by the DT 400 for a duration of about 20-30 seconds at a time, with different DT400 throttles malfunctioning like this at different intervals (I call it a malfunction, but it appears to be a design flaw IMHO). This carrier was strong enough to block the normal traffic that was sent by all other throttles, regardless of proximity to the UR91. I compared three DT 400 throttles that were bought over a span of more than a few years, and all have similar MO, but not identical. One seems to start malfunctioning shortly after going into power save mode, the others typically take up to 20 minutes or more before doing the same. The malfunction continues to cylce like this as long as the
throttles are allowed to stay in the power save mode. Since disabling the PS mode, I have not monitored one incident on my 900mhz radio setup. Looking back the power save mode was annoying anyhow, so I could have saved myself all the grief troubleshooting, by disabling it from the start (lesson learned). I did have one
very brief conversation with Digitrax after my findings regarding, and they did agree on taking the DT 400 out of the PS mode.