8A1. Description. Interior communication (I.C.) systems in a submarine provide the means of maintaining contact, transmitting orders, and relaying indications of the condition of certain machinery or other parts of the ship, to and between various stations in the ship. Each of the systems is designed to perform a specific function such as transmission of voice, transmission of an indication of heat or pressure, the degree of rotation of some device, the open or closed state of a valve, or simple bell or light circuit. Others, such as the underwater log and compass, furnish vital navigational information.

The majority of the systems are electrical and automatic in operation. Some, such as the motor order telegraph system are manually operated but include an electrical circuit for the actual transmission of the order to another part of the ship. Some of the systems operate on alternating current, others on direct current; still others, such as the tachometer and sound-powered telephone systems operate on self-generated current.

The various systems and their components are described in this and following chapters.

The I.C. systems of a modern fleet type submarine usually consist of about 24 circuits. With few exceptions, they are supplied with power through the I.C. switchboard located in the control room.

The following is a list of important I.C. circuits and their circuit designations:

Telephone call system (circuit E)

Engine governor control and tachometer system (circuit EG)

Battle telephone systems (circuits JA and XJA)

Engine order control system (circuit 3MB)

Dead reckoning tracer system (circuit TL)

Collision alarm system (circuit CA)

  General alarm system (circuit G)

Diving alarm system (circuit GD)

Low-pressure lubricating oil and high-temperature water alarm system (circuit EC)

Shaft revolution indicator systems (circuit K)

Gyrocompass system (circuit LC)

Auxiliary gyrocompass system (circuit XLC)

Motor order telegraph system (circuit 1MB and 2MB)

Marker buoy system (circuit BT)

General announcing system (circuit 1MC)

Submarine control announcing system (circuit 7MC)

Rudder angle indicator system (circuit N)

Bow and stern plane angle indicator system (circuits NB and NS)

Auxiliary bow and stern plane angle indicator system (circuits XNB and XNS)

Main ballast indicator system (circuit TP)

Hull opening indicator system (circuit TR)

Underwater log system (circuit Y)

Bow plane rigging indicator system

In addition, the following circuits which are not part of the I.C. systems, are supplied through switches on the I.C. switchboard:

Torpedo data computer (circuit GA-1)

Torpedo data computer (circuit 17GA-1)

Torpedo firing (circuit 6PA)

Torpedo ready lights (circuit 6R)

Target designation system (circuit GT)

8A2. Systems requiring alternating current. The following systems require alternating current for operation:


Self-synchronous operated motor order telegraph and indicator systems (for main propulsion orders)

Self-synchronous operated diving plane angle indicators (bow and stern planes)

Self-synchronous operated rudder angle indicator system

Hull opening and main ballast tank indicator systems

Hydrogen detector

Lubricating oil (low pressure) and circulating water (high temperature) alarm systems

Telephone selective ringing system

General announcing systems (alarm signals and voice communication)

Self-synchronous operated underwater log system

Self-synchronous operated propeller shaft revolution indicator system

Target designation system

  Engine governor control system (direct current on latest submarine)

Torpedo data computer (circuit GAl)

8A3. Systems requiring direct current. The following systems require direct current for operation:

Marker buoy system

Engine order indicator system (alternating current on older submarines)


Auxiliary gyrocompass

Torpedo data computer (17GA-1)

Torpedo firing

Torpedo ready lights

Engine governor control system

Auxiliary bow and stern plane angle indicating systems

Resistance thermometer systems

Gyrocompass system

8B1. Interior communication switchboard. a. Description. The I.C. switchboard is usually located on the starboard side of the control room. The switchboards on the latest type submarines are equipped with snap switches and dead front fuses, with blown fuse indication, mounted directly below or on either side of each switch requiring fuses. Earlier type submarines used knife switches with fuses mounted immediately below each switch.

b. Source of power. The alternating current power supply to this switchboard is obtained from the I.C. motor generators which are comprised of either 250-volt d.c. motors and 120-volt a.c. generators, or 120-volt d.c. motors and 120-volt a.c. generators, depending upon the type of installation. The former would take its power directly from the batteries, the latter from the lighting system. If the supply is taken from the lighting system, the installation is also

  equipped with an emergency supply obtained from a center tap off the battery through a double throw switch, for use in the event of failure of the lighting motor generator set.

The direct current power supply to the switchboard comes from the lighting system. An auxiliary supply of direct current for the gyro compass and torpedo data computer may be obtained from a rectifier which receives its power supply from the alternating current bus.

Fused switches are supplied for the primaries of each of the two 120/8 volt transformers for the 6-8 volt circuits, and for the searchlight. One spare fused switch is provided, wired into the direct current bus, and 2 spare switches are wired into the alternating current bus.

Figure 8-1 is a simplified diagram showing the I.C. power supply system and controls.


Figure 8-1. Simplified diagram of I.C. power supply.
Figure 8-1. Simplified diagram of I.C. power supply.

Figure 8-2. I.C., gyro, action cutout and I.C.
motor generator switchboards, latest type.
Figure 8-2. I.C., gyro, action cutout and I.C. motor generator switchboards, latest type.
8B2. Action cutout switchboard. The action cutout switchboard on the latest fleet type submarines is mounted adjacent to the I.C. switchboard. The action cutout switchboard usually has 6 snap switches (5 active and 1 spare) which are provided to cut out general   announcing circuits from the bridge and conning tower; and 8 rotary switches (7 active and 1 spare) to cutout and transfer the control and indicating stations of the various I.C. circuits between the bridge, the conning tower, and the control room.

Figure 8-3. Action cutout and I.C. switchboards, latest type.
Figure 8-3. Action cutout and I.C. switchboards, latest type.

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