One engine, and two controllers

 Yep that's pretty much normal operation in the Legacy and DCS world.

Remember, with DCS both the app and the remote tell the TIU to send a command to the loco.  The loco doesn't know who told the TIU to do it, and the TIU doesn't care whether the order to send the command comes from the WIU or the remote.

Thanks for the replies, can live with it.

Hi all,

BRIANR has his answer, but for the sake of understanding I thought I might share a little info about DCC that probably lead to his question.  In DCC, much like TMCC and Legacy, you only have one command base (command station in DCC parlance), but you can have many remote controls (a.k.a. cabs).  One of the ways that many DCC systems try to increase robustness is to continuously re-send the last speed command for each engine.  The command station can send commands to over 10,000 locomotive addresses, but it can only keep track of a limited number of locomotive addresses and speed commands (usually 128 or fewer).  To reserve a spot in the command station's memory, you must "acquire" the locomotive by entering its address from a cab.  When you do this the command station associates the locomotive address with the acquiring cab number and only that cab can send commands to that address.  With DCS, TMCC, and Legacy, you can run an engine from a second remote (or app) without any special action, but that's not the case with most DCC systems.  Procedures vary from one brand of DCC system to another, but in most cases you must issue a request to acquire the locomotive from the second cab before you can run it.  On some systems the first cab must relinquish control of the engine before it can be acquired by another cab.  Just to add extra hoops to jump through, many DCC systems require you to physically plug the cab into a hard wired command bus terminal to acquire an engine.  Imagine tethering your DCS remote to the TIU every time you wanted to pick a different engine from the engine list!

The up side to this convention in DCC is that multiple operators usually can't mess each other up.  The down side is that handing off an engine from one operator to another is a bit of a hassle.