"SILENCE on the line" is the most important and frightening statement in the Naval Ordnance community. It means some emergency exists. For instance, a piece of crushed ammunition in the gun loading system, a fire, someone seriously injured, or a major violation of the safety rules.
My friend, Master Chief James Smith, was the senior Gunner's Mate on the USS Missouri. The Captain of the ship was a past commanding officer of mine and one who I did not have glowing reviews for. In any case, the first time they shot the 16"/50 turrets with Jim aboard, they chain of command got to hear "Silence on the line".
It seems, as the story was related to me by Jim, that a number of written, required, safety regulations were not being adhered to for the firing of the turrets. What safety regulations? No fire hoses charged on deck adjacent to the turrets for gun cooling, the intra-turret sprinkler system not charged and ready, and a few others. Just one of these violations of safety would be enough to stop the loading of ammunition. In any case, Jim pronounces "Silence on the line" and everything stopped, as it should. The next thing that Jim heard on the sound powered phones was the Captain yelling; "Who called Silence on the Line?!" Jim replied, I did! The Captain summoned him to the bridge. On the bridge, Jim explained to the Captain the safety requirements for shooting any Naval gun. The Captain informed Jim that they did not adhere to those safety rules on HIS ship because the fire hoses stained HIS teak decks!! Jim told the Captain; "As long as I am on this ship we WILL follow safety!" The Captain then ordered "Flight Quarters" and instructed the helo detachment OIC to fly Jim to Long Beach, and that was that. Jim was transfered off the USS Missouri and a week later, the USS Iowa incident occurred.
The moral of this story is, If you are right, if you can document that you are right, and if the ship is NOT under attack, follow the written rules, enforce the rules, regardless of the consequences! Someone may live because of your vigilance!