1MC is the term for the shipboard public address

Public address

A public address system is an electronic amplification system with a mixer, amplifier and loudspeakers, used to reinforce a sound source, e.g., a person giving a speech, a DJ playing prerecorded music, and distributing the sound throughout a venue or building.Simple PA systems are often used in...

 circuits on naval vessels of the United States. 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 able to (normally) 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

Amplifier

Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...

-oscillator group which is located in the IC/gyro room, a microphone control station, portable microphone

Microphone

A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...

s 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, after steering and Damage Control Central area.

During an incident involving a casualty, the 1MC is a communication tool used by DCA (damage control

Damage control

Damage control is a term used in the Merchant Marine, maritime industry and navies for the emergency control of situations that may hazard the sinking of a ship...

 assistant) 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

Officer of the Deck

Officer of the deck is a position in the United States Navy and United States Coast Guard that confers certain authority and responsibility. The officer of the deck on a ship is the direct representative of the captain, having responsibility for the ship.-Overview:In port, the OOD is stationed on...

, 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

Anti-ship missile

Anti-ship missiles are guided missiles that are designed for use against ships and large boats. Most anti-ship missiles are of the sea-skimming type, many use a combination of inertial guidance and radar homing...

, chemical attack, collision, or a flight deck

Flight deck

The flight deck of an aircraft carrier is the surface from which its aircraft take off and land, essentially a miniature airfield at sea. On smaller naval ships which do not have aviation as a primary mission, the landing area for helicopters and other VTOL aircraft is also referred to as the...

 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
• 18MC - Bridge
• 19MC - Aviation control
• 21MC - Captain's command
• 22MC - Electronic control
• 23MC - Electrical control
• 24MC - Flag command
• 26MC - Machinery control
• 27MC - Sonar
  Sonar
  Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
  
   and radar
  Radar
  Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
  
   control
• 29MC - Sonar control and information
• 30MC - Special weapons
• 31MC - Escape trunk
  Escape trunk
  An escape trunk is a small compartment on a submarine which provides a means for crew to escape from a downed submarine; it operates on a principle similar to an airlock, in that it allows the transfer of persons or objects between two areas of different pressure.-Principle of operation:The water...
  
  
• 32MC - Weapons control
• 35MC - Launcher captains
• 39MC - Cargo handling
• 40MC - Flag administrative
• 42MC - CIC
  Combat Information Center
  The Operations Room is the tactical center of a warship or AWAC aircraft providing processed information for command and control of the near battle space or 'area of operations'...
  
   coordinating
• 44MC - Instrumentation space
• 45MC - Research operations
• 46MC - Aviation ordnance and missile handling
• 47MC - Torpedo
  Torpedo
  The modern torpedo is a self-propelled missile weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with it or in proximity to it.The term torpedo was originally employed for...
  
   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 - SAMID alert

Usage examples

• General Quarters - "General Quarters, General Quarters! All hands man your battle stations. Go up and forward on your starboard side, down and aft
  Aft
  Aft, in naval terminology, is an adjective or adverb meaning, towards the stern of the ship, when the frame of reference is within the ship. Example: "Able Seaman Smith; lay aft!". Or; "What's happening aft?"...
  
   on your port side. General Quarters, General Quarters!" The reason for General Quarters is generally given (such as "Fire in Main Space 2").
• Sweepers - "Sweepers, Sweepers, man your brooms. Give the ship a clean sweep down both fore and aft! Sweep down all lower decks, ladder wells and passageways! Dump all garbage clear of the fantail
  Poop deck
  In naval architecture, a poop deck is a deck that forms the roof of a cabin built in the rear, or "aft", part of the superstructure of a ship.The name originates from the French word for stern, la poupe, from Latin puppis...
  
  ! Sweepers." Most ships actually discourage throwing of trash over the side but instead use mulch/pulp rooms. In port, "Dump all garbage clear of the fantail" is replaced with "Dump all garbage in dumpsters provided for on the pier."
• 8 O'Clock Reports - "Now lay before the mast (if the Captain is on board) all eight o'clock reports. Eight o'clock reports will be received in the wardroom by the Commanding Officer."
• Personnel Working Aloft - "There are personnel working aloft on board (ship), do not rotate, radiate, or energize any electric or electronic equipment, start gas turbine
  Gas turbine
  A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....
  
  s, or operate ship's whistle while personnel are working aloft on board (ship)." Passed every fifteen minutes and by all adjacent ships.
• Divers Over the Side - "There are divers over the side, do not rotate screws
  Propeller
  A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...
  
  , cycle rudder
  Rudder
  A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...
  
  s, take suction from or discharge to the sea or operate any underwater equipment without first contacting the Chief Engineer and the diving supervisor." (Passed every fifteen minutes)
• Men in the Sail (RE: sub tender workers from the Repair Department R3 Division, IC (Interior Communications Electricians) - "There are men in the sail, do not raise or lower, rotate or radiate from any mast or antenna, there are men in the sail." Passed every fifteen minutes.
• Reveille
  Reveille
  "Reveille" is a bugle call, trumpet call or pipes call most often associated with the military or summer camp; it is chiefly used to wake military personnel at sunrise...
  
   - "Reveille! Reveille! Reveille! All hands heave out and trice up. Reveille!"
• Taps
  Taps
  "Taps" is a musical piece sounded by the U.S. military nightly to indicate that it is "lights out". The tune is also sometimes known as "Butterfields Lullaby", or by the lyrics of its second verse, "Day is Done". It is also played during flag ceremonies and funerals, generally on bugle or trumpet...
  
   - "Taps! Taps! Lights out! All hands return to their racks and maintain silence about the decks. Taps."
• Darken Ship - "Darken Ship! Make Darken Ship reports to CCS."
• Fire - "Fire, Fire, Fire, Class (A, B, C, or D) Fire in Compartment (Compartment Number and Nomenclature if known). Away the (at sea fire party (generally called "Flying Squad"), IET (In-port Emergency Team), or ship's fire fighting team) provide from Repair 2 (or closest Repair Station not inside the fire boundary)"
• Breakaway music
  Breakaway music
  Breakaway music is a modern U.S. Naval tradition used to motivate sailors upon the conclusion of underway replenishment UNREP, although using breakaway music is at the discretion of the Captain, and not all commands use it...
  
   - Popular music played at the conclusion of an underway replenishment evolution. It is used to motivate the crew.
• Submarine
  Submarine
  A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...
  
   diving - "Dive, dive." (followed by two klaxon blasts then) "Dive, dive."
• Security Alert - "Security Alert! Security Alert! Away the Security Alert team! Away the Back-up Alert force! All hands not involved in Security Alert stand fast! Reason for Security Alert: (state reason)"
• Flight Quarters - "Flight Quarters! Flight Quarters! Set condition 1-alpha for flight operations! Set condition 1-alpha for hoisting and lowering of boats, port boat davit! The smoking lamp is out aft of frame 1-2-niner; all personnel not involved in flight operations stay forward of frame 1-2-niner! All personnel remove soft hats and refrain from throwing FOD
  Foreign object damage
  Foreign Object Debris is a substance, debris or article alien to a vehicle or system which would potentially cause damage.Foreign Object Damage is any damage attributed to a foreign object that can be expressed in physical or economic terms that may or may not degrade the product's required...
  
   material over the side!"
• "The following is a test of the helo crash alarm from the flight deck - disregard this alarm. (Test alarm sounds) Test complete - regard all further alarms!"

The 1995 film Crimson Tide

Crimson Tide (film)

The film has uncredited additional writing by Quentin Tarantino, much of it being the pop-culture reference-laden dialogue.The U.S. Navy objected to many of the elements in the script — particularly the aspect of mutiny on board a U.S. naval vessel — and as such, the film was produced...

demonstrates in some detail the usage of the 1MC with regard to command instructions and ship-wide orders.

External links

• Authentic Navy Alarm Sounds from policeinterceptor.com List of standardized 1MC phrases