What's Inside Aircraft Jumper Cables?

A friend of mine has some very nice aircraft auxiliary power cables, and
he was going to take it apart and remove the insulation for the scrap
copper. After seeing how nice it is (4/0 stranded cable), he put it back
together, but he noticed something strange. Inside the plug connector
was a 50 ohm resister in series with a diode connected across the two
cables. Copper pins were inserted into the braided wire to make the
connection.

Does anyone know what that is for?

Thanks