I just bought a K-Line K-1116 SF "Steam Chief" Passenger Set. I noticed on the back end where the tender hooks up there is an electrical connector that looks like a sound connector on the back of a computer's CD-ROM drive. There are wires going to it and I can see a circuit board inside the engine. The instructions do not mention this and I did not see anything about it on K-Line's website. Any information would be greatly appreciated. Here's a pic of it.