Metra F40PH-3 question.

[IvanSokolov]

Hi there.
Can someone tell me for what do this little red outlet below headlight is used for?

Thx in advance

 

[JackieG]

Im guessing something to do with the electronics? Im not qualified though.

 

[whitepass]

MU cables.

 

[RRSignal]

Whitepass is correct. There is more info here:

http://www.railway-technical.com/us-musp.shtml