Steam & Diesel question

[battalion51]

Not quite sure if anyone here will be able to answer this question, but I'll give it a whack anyway. I've noticed that a number of today's steam trains run with a diesel trailing to help them make it over the road and provide HEP. My question is how are these diesels run? Is it necessary to have an Engineer in both units with them communicating by radio to discuss how much power they need from the diesel, or have they figured out a way to MU the Diesel to the steam engine so that it works just like a normal MUing when multiple diesels are being used? Any insight would be helpful, many thanks.

 

[Sam Damon]

According to Al Krug, at least one steam locomotive -- SP&S 700 -- had the conventional MU box installed for those reasons you cite.