The SS 393 insignia.

About Submarine
Interior Communications

The SSN 651 insignia.
All ships including submarines have internal communications systems. In general they can be broken down into these categories:
Alarm system
    The alarm system is integrated into the 1MC System. It consists of four signal generator modules, each one producing a specific sound.
  1. General Alarm - A gong sound, used for emergencies and battle stations.
    Duration: As long as necessary, about 6 seconds.
  2. Diving Alarm - A klaxon sound (See below for Diesel boats) - Used for diving and surfacing.  Duration: Diving, sound two times then quit. Surfacing, sound three times then quit.
  3. Collision Alarm - A pulsing siren sound - Used for eminent collision warning.
    Duration: As long as necessary, about 7-10 seconds.
  4. Reactor or Power Plant Alarm - A pair of alternating high and low tones, similar to a European siren. Only on nuclear submarines. Duration: As long as necessary, about 7-10 seconds.
    The Diesel submarines had electric, motor driven, klaxons dispersed throughout the boat. The modern signal is an approximate simulation. The general and collision alarms were generated by electronic modules.

    You can sample four of the alarms below:
    Click here for a General Alarm. (2.6 seconds)
    Click here for a modern klaxon Diving Alarm. (Sounds 2 times, 3.6 seconds)
    Click here for a mechanical klaxon Surface Alarm. (Sounds 3 times, 6.3 seconds)
    Click here for a Collision Alarm. (7.8 seconds)
    Click here for a Reactor or Power Plant Alarm (4.0 seconds).  *It still sounds the same.

    Klaxon   Class H MC Speaker

Announcing systems

1MC General Announcing - Used only as authorized by the O.O.D..

    Submarine General Announcing Groups:
    1. All - Ship wide
    2. Weather Deck Forward (Diesel boats)
    3. Weather Deck Aft (Diesel boats)
    4. Engine Rooms (Diesel boats)
    5. Upper & Main Deck Passages, Mess, Lounges, Galley (Diesel boats)
    6. Lower Deck Passageways, Shaft Alley, Steering Gear Room (Diesel boats)
2MC Engineering Announcing - Propulsion Plant Engineering machinery spaces only

4MC Damage Control 2-way Emergency Reporting Announcing used with the XJA system.
    Various sound powered phone hand sets throughout the ship have 4MC selectors.
    When 4MC is selected the sound powered phone user can broadcast on the 4MC.

Intercom systems

7MC General Announcing 2-way - Ship Control or Maneuvering Announcing

21MC Captain's Command  2-way - Bridge, Conn & other stations

22MC Radio Room / Electronic Control 2-way

27MC Sonar Control 2-way - Sonar Supervisor

31MC Escape Hatch Announcing 2-way

47 MC Weapons - Fire Control & Torpedo Room

On Diesel boats:

    The general announcing system is comprised of two voice communications circuits, one-way (1MC) and two-way (7MC). The same amplifier equipment is used for both circuits. Generally, one channel is used for the 1MC and one for the 7MC, but in an emergency both circuits may be operated through either of the two individual amplifier channels.

Telephone systems

JA, XJA - Sound Powered Phone System (SPT)  Circuits

    The sound powered phone system is a telephone system in which the power comes from the sound of the voice. Vibrations from the voice cause a diaphragm to vibrate. Attached to the diaphragm is a delicate needle, or armature, that is surrounded by a fine wire coil held in place by a magnet. The movement of the armature inside the coil induces current which is transmitted through the line to a receiver. The receiver is constructed exactly like the transmitter. The current from the transmitter passes through the coil on the receiver and causes the diaphragm to vibrate and reproduce the speaker's voice. The system is divided into two circuits, the XJA (handset) used for routine ship's service communication, and the JA (headset) used on all battle control stations.
E - Telephone Call Annunciator System (between SPTs) "Growler" multi-station Intercom

3EM - Telephone Call Annunciator System - Engineering (between SPTs) "Growler" multi-
          station Intercom
    The telephone call annunciator system consists of hand cranked signal generators located in each compartment and require no supply voltage. Often referred to as "growlers" each unit consists of a selector rotary switch used to select the compartment desired and a small speaker that "growls" on the receiver unit to notify the compartment of an incoming call. It is a separate complete circuit and is not connected to the phone systems.
"White Rat" - Speaker system in maneuvering that monitors all engineering spaces
                     sound powered phones.

Dial X - Internal Dial telephone System (nuke boats only, replaced with non-mechanical on new boats)

Indicator systems

The rest of the IC systems are too numerous to mention. Some examples are; Gyrocompass and repeaters, Engine Order Telegraph, Digital Depth Gauge, Bilge alarms, Underwater log, Atmosphere Monitors, Ship's Entertainment systems, Planes and Rudder Angle indicators and, Salinity Cells.


USS Pampanito museum

Battleship New Jersey Amateur Radio Station

Jerry Uffelman IC1(SS) 

*Power Plant Alarm sound verified at T.T.F. Kingsland, GA 7/05


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