1 Main Circuit (1MC) is the term for the shipboard

public address A public address system (or PA system) is an electronic system comprising microphones, amplifiers, loudspeakers, and related equipment. It increases the apparent volume (loudness) of a human voice, musical instrument, or other acoustic sound sou ...

circuits on

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

and

United States Coast Guard The United States Coast Guard (USCG) is the maritime security, search and rescue, and law enforcement service branch of the United States Armed Forces and one of the country's eight uniformed services. The service is a maritime, military, m ...

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 An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost t ...

oscillator Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...

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

microphone A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publ ...

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 The Ood are an alien species with telepathic abilities from the long-running science fiction series ''Doctor Who''. In the series' narrative, they live in the distant future (circa 42nd century). The Ood are portrayed as a slave race, natural ...

stations on the quarterdecks, aft steering and Damage Control Central area.NAVEDTRA 14325 p. 4-14 During an incident involving a casualty, the 1MC is a communication tool used by DCAs (

damage control In navies and the maritime industry, damage control is the emergency control of situations that may cause the sinking of a watercraft. Examples are: * rupture of a pipe or hull especially below the waterline and * damage from grounding (runn ...

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 An anti-ship missile (AShM) is a guided missile that is designed for use against ships and large boats. Most anti-ship missiles are of the sea skimming variety, and many use a combination of inertial guidance and active radar homing. A goo ...

chemical attack Chemical warfare (CW) involves using the toxic properties of chemical substances as weapons. This type of warfare is distinct from nuclear warfare, biological warfare and radiological warfare, which together make up CBRN, the military acronym ...

, collision, or a

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 helicopte ...

crash.

Other circuits

* 2MC: Propulsion plantNAVEDTRA 14325 p.4-15 * 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 A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually someth ...

* 19MC: Aviation control * 21MC: Captain's command * 22MC: Electronic control * 23MC: Electrical control * 24MC: Flag command * 26MC: Machinery control * 27MC:

Sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances (ranging), communicate with or detect objects on o ...

and

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...

control * 29MC: Sonar control and information * 30MC: Special weapons * 31MC:

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 ...

* 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 A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, ...

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, battle stations, or action stations is an announcement made aboard a naval warship to signal that all hands (everyone available) aboard a ship must go to battle stations (the positions they are to assume when the vessel is ...

: "General Quarters, General Quarters! All hands man your battle stations. The flow of traffic is up and forward on the

starboard Port and starboard are nautical terms for watercraft and aircraft, referring respectively to the left and right sides of the vessel, when aboard and facing the bow (front). Vessels with bilateral symmetry have left and right halves which ar ...

side, down and

aft "Aft", in nautical terminology, is an adjective or adverb meaning towards the stern (rear) of the ship, aircraft or spacecraft, when the frame of reference is within the ship, headed at the fore. For example, "Able Seaman Smith; lie aft!" or "Wh ...

on the

port A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as H ...

side. Set material condition lace material condition herethroughout the ship. This is r "is not"a drill." "General Quarters, General Quarters!", "Up and forward", etc., refer to the flow of foot traffic as personnel make their way to their stations; the directions given are standard on U.S. Navy and U.S. Coast Guard vessels. 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 decks, ladders and passageways! Dump all garbage clear of the

fantail Fantails are small insectivorous songbirds of the genus ''Rhipidura'' in the family Rhipiduridae, native to Australasia, Southeast Asia and the Indian subcontinent. Most of the species are about long, specialist aerial feeders, and named a ...

! Sweepers." (Most ships today 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 "Take all trash to the proper receptacles provided for on the pier." * 8 O'Clock Reports: "Lay before the mast all eight o'clock reports. Eight o'clock reports will be taken by the Executive Officer in the Executive Officer's stateroom." When in port Eight O'Clock Reports are normally taken by the Command Duty Officer at a location of the CDO's choosing. * 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 A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...

s r aboard submarines, "raise or lower any mast" 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 A screw and a bolt (see '' Differentiation between bolt and screw'' below) are similar types of fastener typically made of metal and characterized by a helical ridge, called a ''male thread'' (external thread). Screws and bolts are used to f ...

, cycle

rudder A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, aircraft, or other vehicle that moves through a fluid medium (generally air or water). On an aircraft the rudder is used primarily to counter adve ...

s, operate

sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances (ranging), communicate with or detect objects on o ...

, take suction from or discharge to the sea, blow, flood, or vent any tanks, or operate any underwater equipment without first contacting the Chief Engineer and the diving supervisor." (Passed every fifteen minutes) * Men in the Sail (RE: Submarine Tender craftsmen from the Repair Department R4 (Electrical/Electronic Repair) Division, ICs (Interior Communications Electricians)): "There are men working in the sail, do not raise or lower, rotate or radiate from any mast or antenna, there are men working in the sail." Passed every fifteen minutes. *

Reveille "Reveille" ( , ), called in French "Le Réveil" is a bugle call, trumpet call, drum, fife-and-drum or pipes call most often associated with the military; it is chiefly used to wake military personnel at sunrise. The name comes from (or ), the ...

: "Reveille! Reveille! Reveille! All hands heave out and trice up. Reveille!" *

Tattoo A tattoo is a form of body modification made by inserting tattoo ink, dyes, and/or pigments, either indelible or temporary, into the dermis layer of the skin to form a design. Tattoo artists create these designs using several tattooing ...

: "Tattoo! Tattoo! Stand by for evening prayer. Silence about the decks." Given 5 minutes before Taps. * Taps: "Taps! Taps! Out all white lights. All hands turn in to their racks and maintain silence about the decks. Taps." * Darken Ship: "Darken Ship! Make Darken Ship reports to CCS." * Fire: A rapid ringing of the bell on the quarterdeck and then one, two, or three single strokes of the bell are sounded (one for the forward third of the ship, two for middle third, and three for the after third). Then "Fire, Fire, Fire, Class (A, B, C, or D) Fire in Compartment ompartment Number and Nomenclature if known Away the t sea fire party (generally called "Flying Squad"), IET (In-port Emergency Team), or ship's fire fighting teamprovide from Repair 2 (or closest Repair Station not inside the fire boundary)" *

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. When the two ships in ...

: Popular music played at the conclusion of an underway replenishment evolution. It is used to motivate the crew. *

Submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...

diving: "Dive, dive." (followed by two

klaxon A horn is a sound-making device that can be equipped to motor vehicles, buses, bicycles, trains, trams (otherwise known as streetcars in North America), and other types of vehicles. The sound made usually resembles a "honk" (older vehicles) o ...

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: tate 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 material over the side!" * Testing shipwide alarm systems: "The following is a test of the ship's general, chemical, and collision alarms from the bridge --Disregard. est alarm sounds Test complete, regard all further alarms!" * Testing flight deck crash alarm system: "The following is a test of the flight deck crash alert, conducted from the pilothouse, helo control tower, helo control bubble - disregard. est alarm soundsTest sat, test complete. Regard all further alarms!"

In popular culture

* '' Crimson Tide'', a 1995

submarine film The submarine film is a subgenre of war film in which the majority of the plot revolves around a submarine below the ocean's surface. Films of this subgenre typically focus on a small but determined crew of submariners battling against enemy su ...

, demonstrates in some detail the usage of the 1MC with regard to command instructions and ship-wide orders. * ''Battlestar Galactica'' (2003): The series shows frequent use of the 1MC general address system aboard ''Galactica'', most often to warn of an incoming attack. The most typical format for this warning resembles, "Action Stations! Action Stations! Set Condition One throughout the ship! This is not a drill!"

References

External links

Authentic Navy Alarm Sounds
from policeinterceptor.com * List of standardized 1MC phrases {{DEFAULTSORT:1mc Military communications of the United States Equipment of the United States Navy