This was announced on January 7, 1904 by "Circular 57" of the Marconi International Marine Communication Company. It became effective for Marconi installations on February 1, 1904. Another suggestion appeared in the 1906 edition of S. S. Robison's "Manual of Wireless Telegraphy for the Use of Naval Electricians," published for use by the United States Navy. This stated that the standard visual flag signals, known as the International Code of Signals, would likely also be adopted for radio use. Therefore, the flag signal "NC" ( — ·     — · — · ), which stood for "In distress; want immediate assistance", would also likely become the radio distress call.
A third standard resulted in the creation of the SOS distress signal. The German government issued a set of national radio regulations. These were used from April 1, 1905. They introduced three new Morse code sequences, including the SOS distress signal:
SOS was developed from the general German radio call "SOE", with the 3 dits of a "S" easier to hear in static than the one dit of an "E". The string has no other meaning. It was also selected because it is easy to recognize and can be sent rapidly. Comparing SOS (di-di-di-dah-dah-dah-di-di-dit) with the older CQD (dah-di-dah-dit dah-dah-di-dah dah-di-dit) (— ·—· /—— ·—/—· ·) it is obvious how much simpler the new code is. It would not be mistaken for CQ,either. "CQ" is the radio code for "calling anyone" used in casual circumstances.
In 1906, the second International Radiotelegraphic Convention was held in Berlin. This convention developed many Service Regulations to be added to the main agreement, which was signed on November 3, 1906, and became effective on July 1, 1908. Article XVI of the regulations adopted Germany's "Notzeichen" distress signal as the international standard, reading: "Ships in distress shall use the following signal: · · · — — — · · ·  repeated at brief intervals". The first ship to transmit an SOS distress call appears to have been the Cunard liner "Slavonia" on June 10, 1909, according to "Notable Achievements of Wireless" in the September, 1910 "Modern Electrics". However, there was some resistance among the Marconi operators about adopting the new signal, and, as late as the April, 1912 sinking of the RMS Titanic, the ship's Marconi operators intermixed CQD and SOS distress calls. But with the need for consistency for public safety, the use of CQD appears to have generally disappeared after this point.
In both the April 1, 1905 German law, and the 1906 International regulations, the distress signal was specified as a continuous Morse code sequence of three-dits/three-dahs/three-dits, with no mention of any alphabetic equivalents. However, in International Morse three dits make the letter S, and three dahs the letter O, and it soon became common to refer to the distress signal as "SOS." An early report on "The International Radio-Telegraphic Convention" in the January 12, 1907 "Electrical World" said that "Vessels in distress use the special signal, SOS, repeated at short intervals." (In American Morse code, which was used by many coastal ships in the United States through the first part of the twentieth century, three dahs stood for the numeral "5", so in a few cases the distress signal was informally referred to as "S5S").
In contrast to CQD, which was sent as three separate letters with spaces between each letter, the SOS distress call has always been transmitted as a continuous sequence of dits-and-dahs, and not as individual letters. There was no problem as long as operators were aware that "SOS" was technically just a convenient way for remembering the proper sequence of the distress signal's total of nine dits and dahs. In later years, the number of special Morse symbols increased. In order to designate the proper sequence of dits-and-dahs for a long special symbol, the standard practice is to list alphabetic characters which contain the same dits-and-dahs in the same order, with a bar atop the character sequence to indicate that there should not be any internal spaces in the transmission. Thus, under the modern notation, the distress signal becomes SOS. (In International Morse, VTB, IJS and SMB, among others, would also correctly translate into the · · · — — — · · ·  distress call sequence, but traditionally only SOS is used).
SOS has also sometimes been used as a visual distress signal, consisting of three-short/three-long/three-short light flashes, or with "SOS" spelled out in individual letters, for example, stamped in a snowbank or formed out of logs on a beach. The fact that SOS can be read right side up as well as upside down became important for visual recognition if viewed from above.
Additional warning and distress signals were introduced after SOS. On January 20, 1914, the London International Convention on Safety of Life at Sea adopted the Morse code signal TTT ( —  —  —), three letter T's (—) spaced correctly as three letters so as not to be confused with the letter O (- - -), as the "Safety Signal," used for messages to ships "involving safety of navigation and being of an urgent character." When radio transmitters that could send audio were developed, there was a need for a spoken distress phrase, and "Mayday" was adopted by the 1927 International Radio Convention as the equivalent of SOS. For TTT the equivalent audio signals are "Pan-pan" for urgency and "Securite" for navigational safety.
During the Second World War, additional codes were used to include immediate details about attacks by enemy vessels, especially in the Battle of the Atlantic. The signal SSS signalled attacked by submarines, whilst RRR warned of an attack by a surface raider, QQQ warned of an unknown raider (usually an auxiliary cruiser), and AAA indicated an attack by aircraft. They were usually sent in conjunction with the SOS distress code. All of these codes later switched from three repeats of the letter to four repeats ("RRRR", etc.).
Naturalization
Naturalization is when a person changes his or her nationality. Most people have the nationality of the country where they are born and grow up. In other cases, one can be a citizen of a country because the individual in question had a parent, grandparent, etc who was/is a citizen of a different country. If they move to another country they will still keep their own nationality at first, but if they stay there for many years and want to stay there for the rest of their lives they may want to change their nationality.
Different countries have different laws about naturalization. Usually the person must make a promise in a court of law. He will have to promise to be a good citizen and obey the country's laws. Sometimes a country gives citizenship to someone who has not asked for it. Sometimes, someone can keep their first nationality as well as getting a new one. This is "dual nationality". Sometimes children whose parents have different nationalities are allowed to have dual nationality.
Someone who has been naturalized will normally have all the rights that any other person belonging to that country has.
The reverse also happens. States sometimes remove citizenship. This denaturalization can leave the former citizen stateless.
Semaphore line
A semaphore line is an installation used to send optical signals. It is also known as optical telegraph. Common system include signal towers with special installations on them or hand-held flags. The meaning of the signal is determined by the position of the elements, for example the flags. The signal can be read when it is in a stable position. In modern usage, it refers to signalling with a set of flags.
Signal towers came before the electric telegraph. They were faster than sending out post riders with the information.
The following semaphore characters are presented as one would face the flagman:
Ananke group