Newbie to mth

You can run a MTH conventional with LEGACY, but that means changing track voltage so your not going to be able to run the Legacy engines in command mode at the same time very easily.

Legacy does not allow DCS to be connected to it to run MTH, but DCS does allow Legacy base to be connected to it and you can run Legacy and MTH PS-2/3 engines at the same time with the MTH Remote.  G

Get an MTH set-up. You won't be sorry, especially if you plan further expansion.

Dave G.

Use a Track Power Controller hooked to your Legacy box and run them conventionally, separate from your Legacy locomotives. That's the direct answer to your question (and your only option).

Legacy does not have MTH control codes. The only reason it works the other way around is Lionel made Legacy's predecessor TrainMaster Command Control (TMCC) codes public, and MTH was able to build them into their system (by sending those codes to a connected TMCC or Legacy control box), but MTH's own control codes were (and still are) proprietary. 

You can operate Legacy locomotives at the TMCC level using the MTH remote and control box connected to your Legacy box. There is no dedicated remote that "does it all" for both systems. That's just how things developed.

---PCJ 

I see options and what you can and can not do. So what parts of above responses that you don't understand?

Don't hold your breath for that to happen.

Buy a DCS system, connect both to same tracks, then you can run MTH with Legacy.

That would be a 50-1001 DCS system that you will need for access to full features of MTH engines.

I wonder why my answer wasn't good enough.  I don't make things up, and if I didn't know I would not post.    It is what it is.  G

He's a new member, GGG, and may not be familiar with your experience.

bnsftrains,

    GGG is absolutely right, however let me break this down a little more for you.

At this point if you want to run Legacy and MTH engines at the same time and use the Legacy Cab2 controls to due it, you must have both the Legacy 990 base and the Lionel Power Master.  The MTH engines will only run in conventional however.  No Lionel engineering has been developed to convey signal for controlling MTH P2 or P3 engines.

However MTH DCS engineering does accommodate running 95% of the Legacy engine package, via the DCS hand held remote control.  Unfortunately the DCS can not control the wireless FasTrack Command Control switches without the use of the wired up AIU. 

With the DCS package and MTH Z4K with side receiver, you can infact control Legacy & DCS P2/P3 engines both in Legacy mode and Conventional mode, along with controlling P2/P3 and MTH in conventional mode.   Unfortunately no Lionel engineering has been developed to this point for what you would like to do, and as Guns points out, do not hold your breath waiting for it to happen.  GGG in fact advised you that what you want, simply does not exist, and gave you a way to run the different engines on the same tracks.  What you definitely need to do is purchase Barry's DCS O Gauge Companion Book and the OGR Video Guide to DCS, along with watching the Lionel educational Videos starting with Introduction to Legacy.  This will educate you as to the Lionel & MTH Engineering available today.  Even my electrical engineering buddy Billy Ingraham (Willygee) here on the OGR, can not legally develop what you were originally asking for.

PCRR/Dave

You can't play a Sony Video Game in an X Box. Since I also run DCC, I will always find it unfortunate, that O gauge doesn't standardize on control. I get that the speed control and motor designis radically different in O, than in N, or HO, but I will always hope.

We are communicating in a forum. Try not to stress, when someone doesn't like an answer and can't just look at you and say "WAAAHHHHH"

That's what I'd like to do right now, as my layout is so dirty under the tree, I may have to shut down and clean everything. I could post all day and no one is gonna tell me I can just blink the dirt away. I'll stop there, but you get my point.

Set up the dcs system. 

Prepare for life in the big league.