Patent ID: 8005424

Claim:
A communication device of an underwater vehicle, for performing communication between an underwater vehicle in water and an object on land or on water, or between underwater vehicles in water, the device comprising: a code controller that compresses and expands data; a digital modem that modulates and demodulates the compressed data; and a transceiver that transmits/receives the modulated data by the low-frequency electromagnetic field, wherein the device is operable in a plurality of communication modes, including cable communication, wireless communication, optical remote-control communication, and acoustic remote-control communication, wherein the device is switchable from one of the communication modes to another of the communication modes as an optimum communication mode, based on a communication situation, wherein, in the wireless communication, the device is configured to compress data to be transmitted and transmit/receive the compressed data by the use of a low-frequency electromagnetic field, and wherein the transmission/reception by the electromagnetic field is performed at a frequency of 100 kHz or less.