Unidentified object on Conrail GP9

[Green_Elite_Cab]

Most Conrail GP9 photos show a red square object with a hole in the center about under the rear end of the cab. On the photo about under the "7" of the road number. There is also some small white lettering over it. What is it used for?

ps. I miss that red "object" on my Athearn GP9.

http://www.railpictures.net/viewphoto.ph...58&nseq=49

Is that an MRS1 next to that GP9?