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INTRODUCTION

Submarine communications is an important part of the submarine combat system. The communications array on-board a submarine can provide valuable information such as bearing and speed of approaching ships; location and bearing of land targets; notification of bearing and position of the submarine itself to commanding station; and information given from superior command. Submarine communications also provides security, because it allows the president or other high ranking officers to have control over submarines who ,some of them, carry nuclear ballistic missiles. Submarine communications is an essential part of the submarine. It ensures security for the commanding officers, and survival for the men and women operating the submarine.

Submarine communications uses an array of frequencies to communicate. To communicate with a submerged submarine, a transmitting station sends out a signal in the (ELF) range. This range is from 3 - 30 Hz. This low frequency range is used primarily because of its electromagnetic characteristics as it relates with seawater. Its attenuation is small under the surface of the water. unfortunately, this low frequency range has a slow transmission rate. So, the messages sent on this range may just tell the submarine to surface and wait for another signal. The transmitting station of these types of signals are large because the transmitting antenna needs to be large to accomodate the wavelength of the signal. Once the submarine receives the signal and raises to a higher depth. It can then receive a signal from approaching aircraft or other land-based stations. The frequency used not to communicate is in the (VLF) range. This range is from 3 - 30 Khz. The transmission uses a digital modulation scheme representing a binary code of 1's and 0's. The type of scheme could be Amplitude Shift Keying, Frequency Shift Keying, or Phase Shift Keying. Submarine communications uses various frequencies to communicate giving the submarine a dynamic ability and ensuring its security and survivability.