Light language (light communication) is a universal language for communication between ships and is widely used internationally.The term ”lantern language" has a long history.In an era when communication was still underdeveloped, lantern language played a vital role in the field of navigation.Using the flashing frequency of the light to transmit information in binary Morse code can help the crew communicate with each other at a long visual distance.

The signal lights of ships are divided into two types according to their purpose: navigation lights and general signal lights.The on and off times of the signal lights are generally based on sunset and sunrise as the time limit.

Signal light: It is the light sign of a ship under various special circumstances, especially for night navigation, and it is one of the indispensable communication tools.The control of signal lights is generally concentrated in the driving platform, which requires two power supplies.There are many types of signal lights.In order to meet the special requirements of ports and narrow water passages in certain countries, the signal lights of ocean-going ships are more complicated to set up.These signal lights are usually installed on a special signal mast or radar mast on top of the driving platform, and the ring lights of red, green, white and other colors are divided into two or three rows according to the prescribed number (8 to 12).

Navigation light: It is an independent part of the ship's lighting system and an important light signal to ensure the safe navigation of the ship at night.In any case, it must be kept bright to indicate the location, status, type, presence or absence of tugs, etc. of the ship, so as to prevent misunderstandings between surrounding or passing ships and cause general damage accidents.According to international rules, the quantity varies according to the size and length of the ship.For ships with a length greater than 50 meters, five navigation lights should be installed, namely the front mast light, the rear mast light, the rear stern light, and the left and right two side lights.The relevant rules stipulate that in the case of poor visibility, the navigation lights must be turned on at any time, even during the day.

Ship lighting communication uses Morse symbols (Morse), the sender manually manipulates the flash to send, and the recipient receives it visually.Morse symbols use dot code (short) and stroke code (long) alone or in combination to form letters and numbers.The agreed transmission method is: the dot code lasts for 1 unit of time; the code lasts for 3 units of time or more; the interval between the code and the code within the character is 1 unit of time; the interval between the characters is 3 units of time or more.However, in the actual transmission process, there are problems that the length of unit time (or transmission speed) varies from person to person, and random errors cause the length of the dot code (or marking code) to be different.Only after certain professional training can it be sent more standardized and easy to be recognized by the recipient.

However, the transmission and reading of the signal language are obtained and decrypted manually. If there is a lack of professionals, it will have a huge impact on the sailing ships.Since the human visual retention is 0.1-0.4 seconds, the unit length of the flash and shorthand should exceed the human visual retention, which varies with the personal circumstances of the signalmen on both sides.The phenomenon of visual retention is that the speed of light communication is greatly limited.

After modern science and technology have automated the transmission and reception of light signals, it has become possible to use invisible light instead of the original visible light communication.This transformation will make lighting communication more confidential and more concealed.However, the existing optical communication technology is mainly used in land transportation to transmit simple distance and location information between vehicles; however, sea shipping is different from land transportation, and it has the following problems: 1.The distance between ships in sea shipping is much longer than that between vehicles in land transportation, and there are higher requirements for signal propagation distance; 2.Sea communication methods are not as diverse as land communication methods, especially when affected by abnormal factors such as war, bad weather or equipment damage. Therefore, light communication, as a relatively stable communication method, needs to rely on it to transmit more information than in the land environment, so there are higher requirements for signal coding and signal reception.

A class of traffic lights used on modern ships (including offshore drilling platforms) to meet various lighting and signal requirements.It includes three types of marine lighting, navigation lights and signal lights.According to the provisions of international conventions, when a ship is sailing at night, operating or in low visibility, in order to indicate its location, status and type of characteristics, the ship must be equipped with various lamps and lanterns to display various signals in order to identify and avoid.To this end, there are strict regulations on the arc of light, visible distance, chromaticity, shell protection and installation location of navigation lights and signal lights.The design and manufacture of ship lights must comply with ship specifications and relevant provisions of international conventions, and can only be installed and used after being inspected by the ship inspection department and issued a certificate.

As the saying goes: "People have words, and lights have words." Light language is also a communication tool. Ships sailing at sea at night rely on changes in various lights to communicate and communicate to ensure the normal and orderly passage of ships.