My Atlas RS-3 is Canadian National #1812 and is a very nice running locomotive on DC. However, I’m running DCC so I needed it more functional.
My decoder brand of choice is TCS, with their “goof-proof” warranty and their “dithering” function for ulta-low speed crawl. In this instance I happened to have on-hand a TCS M3 decoder, which has motor control and 3 functions for things such as lights. I’d only be needing two of the functions but the third is there in case I want to put a strobe light on the roof.
Atlas RS-3 Decoder Install