NASA Photo ID: KSC-72P-111
Date taken: 04/11/72

Apollo 16 astronauts (l-r) John W. Young and Charles M. Duke, Jr., during an EVA exercise in preparation for their lunar landing. Young extracts a cable from its protective package while Duke watches. The cable will connect the RTG, which is seen in the foreground, to the Central Station.

Source: http://images.ksc.nasa.gov