Looking through the Museum of Transportation's collection, I noticed on the 1522, it said... St. Louis-San Francisco ("Frisco") #1522 Baldwin/1926 S Mountain Equipped with booster and diesel multiple-unit control 4-8-2 http://transportmuseumassociation.org/rail_motive_power.htm What exactly does that mean? Could 1522 control attached diesels? Could attached diesels control 1522? Does it just mean that Diesels could communicate through 1522? Was it something done by the SLSTA? Was it something done by Frisco? I'm interested in your knowledge about this. ThomasF.