In some cases, the ships radio room has been brought back into use, with volunteers operating amateur radio equipment. Often, the callsign assigned is a variation on the original identification of the ship. For example, the submarine , which had the call NBQV, is now on the air as NB9QV. The World War II submarine , berthed at the San Francisco Maritime National Historical Park, had the wartime call NJVT and is now on the air as NJ6VT. In other cases, such as , a distinctive call (in this case KH6BB) is used. This radio work not only helps restore part of the vessel, but also provides worldwide publicity for the museum ship.