1 Main Circuit (1MC) is the term for the shipboard public address circuits on United States Navy and United States Coast Guard vessels. This provides a means of transmitting general information and orders to all internal ship spaces and topside areas, and is loud enough that all embarked personnel are (normally) able to hear it. It is used to put out general information to the ship's crew on a regular basis each day. The system consists of an amplifier-oscillator group which is located in the IC/gyro room, a microphone control station, portable microphones at each control station and loudspeakers located throughout the ship. Control stations for the 1MC announcing system are located at the pilot house, OOD stations on the quarterdecks, aft steering and Damage Control Central area. During an incident involving a casualty, the 1MC is a communication tool used by DCAs (damage control assistants) to keep ship members alerted and informed of casualty location area, status, and incident response efforts by the DC organization. The 1MC is divided into smaller sub-circuits, such as officer's quarters and topside. At the option of the officer of the deck, some details are not passed on certain circuits. The 1MC is also used for transmitting various alarm sounds to alert the crew of specific impending dangers such as an inbound anti-ship missile, chemical attack, collision, or a flight deck crash. Other circuits 2MC: Propulsion plant 3MC: Aviators 4MC: Damage control 5MC: Flight deck 6MC: Intership 7MC: Submarine control 8MC: Troop administration and control 9MC: Underwater troop communication 10MC: Well Deck 18MC: Bridge 19MC: Aviation control 21MC: Captain's command 22MC: Electronic control 23MC: Electrical control 24MC: Flag command 26MC: Machinery control 27MC: Sonar and radar control 29MC: Sonar control and information 30MC: Special weapons 31MC: Escape trunk 32MC: Weapons control 35MC: Launcher captains 39MC: Cargo handling 40MC: Flag administrative 42MC: CIC coordinating 44MC: Instrumentation space 45MC: Research operations 46MC: Aviation ordnance and missile handling 47MC: Torpedo control 50MC: Integrated operational intelligence center 51MC: Aircraft maintenance and handling control 53MC: Ship administrative 54MC: Repair officer's control 55MC: Sonar service 58MC: Hangar-deck damage control 59MC: alert Usage examples General Quarters: "General Quarters, General Quarters! All hands man your battle stations. The flow of traffic is up and forward on the starboard side, down and aft on the port side. Set material condition [place material condition here] throughout the ship. This is [or "is not"] a