Hi all, I have been lookin at slugs for awhile and was wondering what makes some of them run. I know the NS SW1200 slugs are powered by a diesel engine and that some other ones like the flat body slug don't have an engine. I was wondering how especially the flat dody slugs run. I was told they feed off the power from the main locomotive, and iv'e also been told they have a battery of some kind. They are booster units I know, but for what specific job? I'm just plain curious thats all.