Switch inside of the Acela engine

[Billm10454]

There is a switch inside of the acela enging marked SW1. What is it for. I am asking because I got this on ebay and the seller said it did not run. I switched the swith to the other position and it ran. I just want to know what the switch is for.

[Mike]

In one position, the engine runs from track power. In the other position the engine runs from overhead catenary.