The two small white receptacles are for the DTN system, which will replace both the communications and traction jumpers. It will also no longer require cars to all face in the same direction so that the jumper recptacles are on the same side. Coaches only have one on either side, and so must all face the same way for the jumpers to connect properly.
Only one of the two white receptacles is used. The other is just used to hold the free end of an unused cable, and is named after me -- dummy.
Proven Theory #2 - If you don't work for the railroad, you don't know more than the people who do, no matter how many years you've hung around the tracks, or how well you think you understand railroading.
Rest in peace Jtgshu.