The alarm system is integrated into the 1MC System. It consists of four signal
generator modules, each one producing a specific sound.
- General Alarm - A gong sound, used for emergencies and battle
Duration: As long as necessary, about 6 seconds.
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.
- Collision Alarm
- A pulsing siren sound - Used for eminent collision warning.
Duration: As long as necessary, about 7-10 seconds.
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
The Diesel submarines had electric, motor driven,
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
Click here for a mechanical klaxon Surface Alarm. (Sounds 3 times,
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.
1MC General Announcing - Used only as authorized by the O.O.D..
Submarine General Announcing Groups:
2MC Engineering Announcing - Propulsion Plant Engineering machinery spaces only
- All - Ship wide
- Weather Deck Forward (Diesel boats)
Weather Deck Aft (Diesel boats)
- Engine Rooms (Diesel boats)
Upper & Main Deck Passages, Mess, Lounges, Galley (Diesel boats)
Lower Deck Passageways, Shaft Alley, Steering Gear Room (Diesel boats)
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.
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.
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-
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
sound powered phones.
Dial X - Internal Dial telephone System (nuke boats only, replaced with non-mechanical on new boats)
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