By Robert E. Straub - KC2AIO <kc2aio@juno.com>

Submarine Interior Communication Systems

     INTERIOR COMMUNICATIONS SYSTEMS include the general announcing system, alarm systems, sound powered phones, and telephone call system.

     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.

     The alarm system is made up of three alarms: the diving alarm, collision alarm and the general alarm. The diving alarm is a series of motor driven alarms located throughout the submarine with a distinctive "ah-oo-ga" sound. Both the general alarm and the collision alarm are produced by signal generators located in the amplifier stack and sound through 1MC speakers or horns in each compartment. The general alarm is a gong sound at 100 beats a minute that is sounded for ten seconds. The collision alarm is a rising siren signal.

     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.

     The telephone call system consists of hand cranked signal generators located in each compartment and require no supply voltage. Often refereed 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.