What does ® mean in the Chart Supplement (A/FD)?
According to the Chart Supplement (formerly the A/FD) legend:


  APP CON—Approach Control. The symbol ® indicates radar approach
  control


And:


  DEP CON—Departure Control. The symbol  ®  indicates radar departure
  control.


The FAA has different approach facilities classifications, a TRACON has radar but others don't. So you should see this symbol when the approach/departure services are provided by a TRACON or other radar facility.