multiple diesels

When 2 or more diesel units are m.u.'d together with the cabs facing opposite directions,how does the unit(s) being controlled know which way is forward or backward?Sent this to "ask trains"months ago but haven’t seen a reply yet.Any engineers out there? Ron Marseilles Il.

On the back wall of the cab there is a switch, more like switchs that control the MU. One sets the unit to be controled from the front or back. Others are lead/trailing, dynamic brakes, and trailing head light

gwl
http://photosbygreg.20m.com

Here is a web page that has photos from inside some cabs showing all the controls, about half way down the page is the MU controls.
http://krugtales.50megs.com/rrpictale/cabtour/cabtoura.htm

gwl

Thanks for the info and website.I always wondered what had to be done to make them run front to back like that,toured a few cabs at museums but I guess I didn’t pay close enough attention. Ron