It was invented by an English inventor named Alexander Bain in 1843. However, fax communication is a relatively slow-developing technology in the field of telecommunications, which gradually matured in the 1920s and developed rapidly after 1960s. In recent ten years, it has become one of the most widely used communication tools.
Enlightenment of pendulum
The origin of fax technology is very strange. It is not the result of intentionally exploring new communication means, but comes from the study of electric clocks. 1842, Alexander Bain, a scot, researched and made a pendulum structure controlled by electricity, with the purpose of forming several clocks that are interrelated and synchronized, just like the master-slave system of the mother-child clock now. In the process of development, he keenly noticed a phenomenon that the pendulum of each clock in this clock system is in the same relative position at any time.
This phenomenon makes the inventor think that if the main pendulum can pass through a figure or character composed of electrical contacts in its journey, then this figure or character will be copied at one or several positions of the remote main pendulum at the same time. According to this idea, he added a scanning needle to the pendulum as a brush; In addition, a clock-driven "information board" is added, which has graphics or characters to be transmitted and consists of electrical contacts; There is an electric sensitive paper on the "information board" at the receiving end. When the pointer scans on the paper, if there is a current pulse in the pointer, a black spot will appear on the paper. When the pendulum of the transmitter swings, it sends out a pulse when the pointer touches the contact on the information board. Driven by the clock, the information board moves up slowly, so that the pointer scans line by line on the information board, and the graphics on the information board become electric pulses and are transmitted to the receiving end; The information board at the receiving end also moves slowly under the drive of the clock, thus leaving a pattern on the photosensitive paper, forming the same pattern as that at the sending end. This is a fax machine with an original electrochemical recording method.
Drum fax machine
1850, there was an English inventor named F. Becker, who greatly improved the structure of the fax machine. He replaced the clock and pendulum structure with a "roller and screw" device. This improved structure works a bit like a lathe, where the roller rotates rapidly and the manuscript sent by fax rotates on the roller. The scanning needle advances slowly along the screw along the axial direction of the drum, and scans the pattern on the surface of the drum in a spiral manner. This drum fax machine has been used for more than one hundred years. 1865, an Iranian named Abakaj developed a fax machine that he could use in practice according to the principle and structure of fax machine proposed by Bain and Bekkar, and took his fax machine to Paris, Lyon, Marseille and other cities in France for fax communication experiments.
The invention of photo fax machine
People have a wide range of requirements for the transmission of news pictures and photographic pictures. Many scientists devote themselves to the research of photo fax machines. 1907165438+1On October 8th, a French inventor, Edward Belin, presented his research achievement-photo fax. Edward Belin (1876- 1963) works in the building of the French Photographic Association, and under the building of the French Photographic Association, it happens to be the starting point and ending point of the French telecom line from Paris-Lyon-Bordeaux-Paris. This provides a unique condition for Belan's research.
Belan's painstaking research has obtained permission from the telecommunications department to use this communication line for experiments at night. Beran studied and experimented in the basement of the building for three years, and finally made a photo fax machine. Not satisfied with his initial success, Edward Belin continued to study the fax machine. 19 13 years, he made the world's first portable fax machine for news interview. 19 14, a French newspaper published news photos transmitted by fax for the first time.
Photo fax changes pointer contact scanning into photoelectric scanning, which not only greatly improves the fax quality, but also makes photo fax possible with the cooperation of photoelectric scanning and photographic plate making.
1925, Bell Research Institute of AT&T Company developed a high-quality photo fax machine. 1926 officially opened the transcontinental wired photo fax service, and in the same year opened the transatlantic wireless photo fax service with Britain. Since then, countries in Europe, America and Japan have successively opened photo fax services. Since then, photo fax has been widely used in news organizations to transmit news photos, and then extended to the military, public security and medical departments to transmit military photos, maps, criminal photos, fingerprints, X-rays and so on.
Color fax machine
The earliest pictures recorded by color fax were published in the first illustration of Bell System Technical Report in April 1925. In fact, this picture is composed of three independent transmissions by color filters in the order of red, green and blue, and then superimposed. Later, someone used the same basic technology and took some automation operations to develop a fax device that can copy color pictures. 1In August, 945, at the Potsdam Conference, the color photos of Truman, Stalin and Attlee were successfully transmitted from Europe to Washington by radio. But it has not been used to open color fax service. It was not until the mid-1980s that the color fax machine gradually developed to a practical level.
The Great Development of Fax Communication Service
From 65438 to 0968, the United States took the lead in opening the fax service on the public telephone network, and countries all over the world also opened the fax communication service by telephone network one after another. The number of fax machines, which were originally limited to special circuits, has surged, and the scope of application has expanded rapidly. In particular to a document fax machine used for transmitting handwritten, printed or printed letters, documents, forms, graphs and the like. Is the most commonly used and fastest growing. Document fax machines used on CCITT telephone network are classified as follows:
Production standards for fax machines now and once sold in the market:
Primary computer (G 1): transmit a page in A4 format (210mm&# 215; 296mm) file about 6 minutes;
Class II computer (G2): It takes about 3 minutes to transmit a page of A4 file during a call;
Class Ⅲ computer (G3): it takes about 1 minute to transmit a page of A4 file during a call;
The fourth type of machine (G4): high-speed document fax machine, which can transmit an A4 document within 3 seconds.
Before the 1970s, the first type of computer was mainly used. In the 1970s, a second type of computer was used. In the 1980s, the third kind of computer became popular. With the continuous improvement of its performance and function, it has gradually become the main computer type for fax communication. The use of four kinds of machines is still not common.
In recent ten years, fax communication has developed more rapidly, and now it has become one of the fastest-growing non-voice telecommunications services.
At ordinary times, we often see words such as "fax photos of Xinhua News Agency" in newspapers, indicating that the photos were sent back by Xinhua News Agency reporters after shooting abroad or elsewhere. If there is no fax machine, it will only be transported by post, which will take three to five days as soon as possible and half a month as slow as possible. At that time, the news published in the newspaper will become "old news"
The history of fax machine is not later than that of telegraph. As early as 1843, before Morse's first telegraph line was set up, Scottish electrical engineer Alexander Bain invented the first fax machine. Bain's fax machine uses electromagnetic excitation pendulum to scan, and the top of the pendulum is equipped with a brush. By swinging the pendulum back and forth, it scans the metal words written on the telegraph desk. When receiving, the paper soaked with starch solution is scanned with a metal brush, and a color record is generated through chemical reaction. From 65438 to 0848, Bakewell further developed Bain's fax technology. His most outstanding contribution was the invention of barrel scanning technology, which has been in use ever since. From 65438 to 0857, the Frenchman Kezley conducted fax communication experiments between Paris and Lyon, and between Paris and Marseille. The content of the experiment is the transmission of photos.
Fax technology has not made great progress for more than half a century. The reason is that some key devices, such as photoelectric conversion devices and signal amplification devices, are not available or very imperfect at present. It was not until the triode, photovoltaic cell and light-emitting tube were developed that the fax machine really went out of the laboratory and entered the practical stage. 1925, Bell Laboratories of AT&T Company developed a practical fax machine by using vacuum tube technology and photoelectric cell technology, and in the second year, it opened a wired photo fax service across the American continent.
The principle of Bell Laboratories' fax machine is as follows: the sending end rolls the sent image on the drum of the fax machine and rotates while moving horizontally, and the light spot scans back and forth line by line on the image, covering the whole picture and decomposing the image into several continuous points. The light spot shines on different parts of the image and reflects light with different intensities. The reflected light is received by the photocell and converted into electrical signals with different intensities, then modulated, amplified and sent to the transmission line. The receiver functions as a composite image. After amplification and demodulation, the input signal is added to the glow tube and then converted into light spots with different intensities. There is also a drum at the receiving end, and the rotation and movement of the drum are synchronized with the sending end. The drum is equipped with photosensitive recording paper, and the light spot converted by glow tube shines on the photosensitive paper. Because the drum rotates synchronously, the recording paper is exposed point by point and line by line, forming a fax image similar to the sent image.
The function of fax machine was fully demonstrated in World War II. Newspapers are scrambling to use fax technology to send news photos, so that people in the rear can see the fighting situation of soldiers in front in time. Therefore, after World War II, fax technology entered an era of rapid development.
Fax machine is "remote copying" in layman's terms. At present, the development trend of fax machine is: the transmission speed is faster and faster, the transmitted images are clearer and clearer, the operation mode is simpler and simpler, the equipment is smaller and smarter.