I think I finally figured out the difference. Lash Up is the term for Toy Train engines and Multiple Unit is for Model Trains ��
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Multiple unit is prototype. Can also be used for toy and model trains. Lot's of people use lash up for all locomotives, real and model. Rich is going to have fun with this one. 
This is the way I use these terms on this forum:
Double (or triple/etc) Headed. Each engine has an engineer and almost always for steam engines, or steam and diesel together (not sure what to call a steam engine and a remote controlled diesel helper controlled from the steam engine cab). However, there were some early diesels that could not be MUed, so two of them together would also be double headed. I use this term when posting or replying to pictures and operational discussions.
MU or consist. Multiple diesels that our electrically/hydraulically connected together and all controlled by one engineer. As above, I use this term when posting or replying to pictures and operational discussions.
Lashup. When discussing electronically connecting two or more command control (either DCS or Legacy/TMCC) toy engines (any type) and running them together with one handheld. I use this term when specifically talking about connecting command control trains together and for obvious reasons usually only on the three rail, DCS or Legacy forums.
Just a couple days ago I did a lashup of two MTH DCS engines, one at the front of a long train and one at the rear. I have done it before but I always forget exactly how to do it as "Lashup" is hidden several menus deep in the DCS controller. I dug out the DCS TIU instructions and set it up easy as pie. It worked fine and I ran it for some time that way without one problem. DCS is very good for lashups. I had done several lashups as multiple engines before but never with one as an end of train pusher. I don't know how hard it is on the two Lionel digital control systems but it could not be easier than the DCS.
LDBennett
1:1 trains call it MU. O gauge command control systems call it a lashup.
See that dead horse in the cprner of the barn,
lets beat him until he stands up and pulls this plow.
lets beat him until he stands up and pulls this plow.
