Classification of telegrams

Telegrams can be divided into many categories due to differences in decoding, transmission speed, information content, etc.

(—) Plain code telegram and cipher telegram

The transmission of certain messages by telegram is not directly sent and received, especially messages written in Chinese characters, and the text needs to be translated into Only the code that can be conveyed by electrical signals can be sent out using a transmitter. Codes are agreed upon by the whole society, and also agreed upon by individuals or groups. The code agreed upon by the whole society is for public use and is called clear code; the code agreed upon by a few individuals or groups is mainly used for confidential activities, so it is called password.

The telegrams sent and received by the public on a daily basis are all clear telegrams. Nowadays, the translation of clear telegrams is usually done by the business personnel of the telecommunications bureau. The sender can write the prepared message according to the procedures prescribed by the postal and telecommunications bureau and hand it over to the business personnel. The telegram received by the recipient is already a business The personnel translated the received telegram into text messages.

(2) Ordinary telegram and urgent telegram

The difference between ordinary telegram and urgent telegram lies in the length of delivery time. As far as the telegram delivery conditions in our country are concerned, ordinary telegrams can generally be received within two to eight hours. However, ordinary telegrams are not sent at night. If the matter is particularly urgent and the speed of ordinary telegrams cannot meet the needs, an urgent telegram must be sent. Urgent telegrams are faster than ordinary telegrams, and the charges are correspondingly higher. When going through the sending procedures, you must write "urgent service" and pay the fee as "urgent service".

(3) Official telegrams and private telegrams

Telegrams are divided according to their content. First of all, they can be divided into two categories: official telegrams and private telegrams. Official telegrams are sent for official purposes. The writing of official telegram manuscripts belongs to the official document genre. Please refer to the relevant chapters on official document writing. Private telegrams are commonly used in personal life communication activities. The writing of this type of telegram manuscript belongs to the scope of daily life practical writing.

There are two main types of electrical codes

Morse code

Morse code consists of short and long electrical pulses called dots and dashes. composition.

The length of time for dots and strokes is stipulated. One point is a basic unit, and one stroke is equal to the length of three dots. Within a character, the interval between dots and dashes is the length of one dot, and the interval between characters is the length of three dots. The space between words is five dots in length. The length of each character in Morse code is different, so it is an uneven code.

The five-unit code

is a uniform code. Each character is composed of five electrical pulses of equal length. Generally, there is current to represent a signal, and no current to represent a blank signal. Pass number and empty number are two different states, and there are only five positions available for selection, so there can be 25 or 32 different combinations. These combinations can represent letters, numbers, punctuation marks, and "functional" combinations. The conversion of letters and numbers is controlled by a combination of functions. There is more than one five-unit code, and the more commonly used ones are the International Code No. 2 and the Digital Protection Code.

Taking the teletype machine as an example, among the 32 combinations of five-unit codes, 26 are used to represent all letters or 26 are used to represent numbers and punctuation marks, and the remaining 6 are functional combinations , the six function combinations are letter digits, numeric digits, line feed, carriage return, space and blank.

There are two main types of telegraph transceivers

Morse code telegraph machines

Morse code is sent by the operator using electric keys. The electric key is actually a switch that is easy to operate for a long time. The point or stroke is determined by the length of time the key is pressed. The telegraph receiver draws symbols of different lengths on the paper tape that advances at a constant speed, or uses sound and other methods to display the received telegram code, and the telegraph operator records the character message. This method of notification is called manual telegraphy. Although manual telegraphy is an early method with a low reporting rate, the equipment is simple, the quality of the transmission circuit is not required, and the operation is relatively stable, so it is still used today.

In 1858, a high-speed automatic telegraph machine using Morse code appeared.

The sending office uses a special punching machine to punch out circular holes corresponding to the message characters on the paper tape, and then sends the punched paper tape on the Morse code automatic telegraph machine. The receiving office uses ripples to receive the message. The machine records dot-and-dash codes on paper tape, and its reporting speed can be several to 20 times faster than manual reporting.

Five-unit code telegraph machine

A teletypewriter is a telegraph machine that uses a five-unit code. It appeared in the 1920s and has been widely used since the early 1930s and developed rapidly. Teletypewriters are similar in appearance to foreign language typewriters. Since the time required to send or receive any character is the same, the design and construction of the machine can be simplified. The teletype machine mainly consists of two parts: a sending keyboard and a receiving printing part, so it has both sending and receiving functions. The transmitting part uses a keyboard equipped with typing keys to send out an electrical pulse signal of five units of electrical code; the receiving part prints characters on the paper page (or paper tape) according to the received electrical code signal, eliminating the need for electrical codes and characters. Manual translation is used between them, so it is efficient and easy to use.

When teletypewriters report, the transmitters and receivers at both ends must work synchronously, synchronizing each time a character is transmitted. Therefore, a space start pulse is added before the first pulse of the five-unit telegraph code of each character, and its length is the same as a signal pulse; and a sign stop pulse is added after the fifth pulse. , its length is usually 1.5 signal pulses. So the actual length of each character is 7.5 pulses. The function of the start pulse and the stop pulse is to make the teletype machine start and stop once each time it sends and receives a character, so as to ensure that the teletype machines at the sending and receiving ends can be synchronized during notification, so the teletype machine is also called It is a start-stop telegraph machine.

In addition to letters, there is a number or symbol on each character position of the receiving and printing device. After pressing the "letter position" function key on the sending keyboard, only the printing part of the receiving newspaper can be printed. letters; and after pressing the "numeric digit" function key, only numeric symbols will be printed in the reporting part. There are 26 types of printed letters or numeric symbols, so the teletype machine can print 52 types of characters. On August 28, 1850, two British brothers, John and Jacob Brett, died at Cape Gris-Nez in France and Cape Solan in England. The tugboat "Giant" was used to lay the first submarine cable in the Dover Strait between Britain and France in the high seas between Souther-land), but it was interrupted after only a few telegrams were sent because of a fisherman. He hooked up a section of cable with a trawl net and cut off a section. He happily showed off this rare "seaweed" specimen to others, saying in amazement that it was filled with gold.

On August 5, 1858, the first submarine cable telegraph crossed the Atlantic Ocean. The Atlantic submarine cable was laid from Valentia on the west coast of Ireland on August 7, 1857. On August 17, the cable broke under 12,000 feet of water. Late at night on July 28, 1858, the two cable-laying ships met again in the middle of the Atlantic Ocean. After splicing the cables, the cable-laying ships laid the cables in opposite directions. On August 5, the cable laying with a total length of 3,240 kilometers was completed. At 2:45 a.m., the first submarine cable message crossed the Atlantic Ocean. A submarine cable telegram was broadcast between the United States and the United Kingdom on August 12. At 1 o'clock on September 3, the cable insulation broke down and was damaged due to the operator's error. The 1909 Nobel Prize in Physics was awarded to Italian physicist Guglielmo Marconi (1874-1937) of the Marconi Wireless Telegraph Company in London, England, and Karl Braun of the University of Strasbourg in Alsace, Germany. Braun, 1850-1918) for their contribution to the development of wireless telegraphy.

The telegraph is the product of human society’s development to capitalism and its urgent need for fast communication over long distances. In the first half of the 19th century, many scientists were engaged in inventions and creations in this area. Morse successfully invented the electrical code in 1837, and soon established long-distance communication networks and transatlantic cables. But setting up wires and laying cables is very time-consuming.

Wouldn't it be more convenient if information could be transmitted directly without going through wires and cables? So wireless telegraphy came into being. However, the emergence of a new thing is not always smooth sailing. Before Marconi and Braun, there had been many attempts to use electromagnetic waves to transmit information: for example: France's E. Blanly, Britain's O. Lodge, New Zealand's Rutherford (E. Rutherford and M. Tesla in the United States have all made useful attempts at wireless communications. Russia's Popov also publicly performed his radio transceiver, but did not receive the support it deserved. Marconi was luckier, and his invention received official support from the British government in a timely manner. In 1895, he successfully conducted radio wave transmission experiments in his garden, and obtained a patent the following year. In 1898, a cross-sea wireless telegraph test was successfully conducted on both sides of the English Channel, with a communication distance of 45 km. The transatlantic wireless telegraph experiment took great risks. At that time, many people believed that radio waves should propagate in straight lines like light, but the Atlantic Ocean spans 2,000 nautical miles (3,700km), and such a curved surface of the earth would not be able to directly transmit radio waves anyway. However, Marconi had a unique vision. Based on the successful practice of long-distance radio waves and the fact that one end of the transmitting station was grounded, he firmly believed that it was possible to make directional radio waves propagate along the earth's surface. In October 1900, a powerful transmitting station was built in the UK, using a 10kW acoustic spark telegraph transmitter. In December 1901, Marconi used a kite to pull an antenna in Canada and successfully received wireless telegraphs from across the Atlantic. News of the successful trial shocked the world. Starting in 1903, news was transmitted by radio from the United States to the British "Times" and appeared in the newspaper on the same day. By 1909, wireless telegraphy had already played a significant role in communications. After that, most of the military fortresses and harbor ships in many countries were equipped with wireless equipment, and wireless telegraphy became a global undertaking. Therefore, Marconi and Braun won the Nobel Prize in Physics. The following is a brief introduction to their lives.

Marconi was born on April 25, 1874 in Bologna, Italy. He is the second son, his father is an Italian country gentleman named Giuseppe. Marconi's mother's name was Anne. Jimson is a native of Duffin City, County Xxford, Ireland. His father is Andrew. jimson. Marconi received private education in Bologna, Florence and Leghorn. As a teenager, he had a strong interest in physics and electricity, and read the works of Maxwell, Hertz, Righi, Lodge and others. Marconi began his laboratory experiments in 1895 at his father's estate in Pontecchio. Here he successfully sent radio signals to a distance of 1.5 miles (2.4km), and he became the inventor of the world's first practical wireless telegraph system.

Braun June 1850 Born on the 6th in Fulda, Germany. He received his education at the local high school here. He studied at the University of Marburg and the University of Berlin, graduating in 1872. His graduation thesis was about the vibration of elastic strings. Later he served as an assistant to Professor Quincke at the University of Würzburg, and in 1874 he was hired to teach at the St. Thomas Gymnasium in Leipzig. Two years later he was appointed as a non-staff professor of theoretical physics at the University of Marburg, and in 1880 he was appointed to the same position at the University of Strasbourg. In 1883 Braun became a professor of physics at the Technical University of Karlsruhe, and in 1885 he was hired to teach at the University of Tübingen. One of his tasks here was to establish a new institute of physics. He did not accept the invitation of the University of Leipzig to succeed Weidmann, but returned to Strasbourg 10 years later in 1895 as director of the Institute of Physics.

In 1898, he began to engage in research on wireless telegraphy, trying to use high-frequency current to transmit Morse signals through water. Later, he applied closed oscillator circuits to radio telegraphy, and was one of the first experimenters to make radio waves emit in a certain direction.

In 1902, he successfully used a directional antenna system to receive directional transmitted signals.

After the outbreak of World War I, Braun was sent to New York to serve as a witness in a patent claim lawsuit. Due to his absence from his laboratory and his illness, it was not possible to continue scientific work. Braun spent his later years quietly in the United States, where he died on April 20, 1918.