FACT: When Apollo astronauts were not in space, they were manning mission control communication for other Apollo missions, this was to limit the number of persons in the know. There were in fact two communication links to every Apollo mission. First was launch control who dealt with communication at lift off, and re entry, however once in Earth orbit communication was handed over to the limited few astronauts manning mission control.
Check it yourself on film coverage released at the time. Collins, Duke, Aldrin, Young, Borman, Armstrong, Lovell, Shepard, Schmitt, Cernan etc, are all there on various missions. Lovell himself admitted that there were two communication links to the astronauts.