On February 14, 1876, the American Graham Bell files the patent forinvention of the telephone. Considered as an improvement of the telegraph which has become speaking, this invention marks the beginning of a new era, that of globalization. Distances are abolished, and time becomes universal. The principle of the telephone was described in 1854 in France byCharles Bourseul, employee of the Telegraph administration, who published in the newspaper "l'Illustration" an article describing a device for conversing at a distance. At the time, he was not taken seriously ...
Graham Bell, inventor of the telephone
Alexander Graham Bell, a young Scottish immigrant to the United States, took an interest in acoustics and taught speech to mutes in Boston. It is by considering the limits of the electric telegraph that he envisions a device capable of reconstituting a normal mode of communication using speech and hearing. Familiar with electromagnetic techniques, he is also interested in devices that use sound waves. This is how he tries to reproduce the internal structure of the ear, successfully, by transforming an acoustic wave into electric current through a vibrating metal blade.
Alexander Graham Bell deposits the patent for his telephone system in March 1876, three hours before his compatriot Elisha Gray patented an equivalent device capable of transmitting voice. For more than ten years, a legal battle opposed Bell and Gray in front of the courts, which finally gave reason to this first. The telephone experienced an immediate boom and was quickly equipped with a microphone, invented by the British American David Hughes in 1881.
Bell will also be at the origin of the American Telephone & Telegraph (A.T.T), the largest private company in the 20th century, sitting on a virtual monopoly in the United States. This power has worked a lot for the myth of this invention. This is a fair return: it is precisely on his status as the inventor of the telephone, and not of a telephone among others, that the fortune of this company was built.
Principle and evolution of the telephone
When you speak into the microphone imagined by Bell, a membrane vibrates: this causes the oscillation of a magnet and therefore the modification of its magnetic field. The magnet produces an electric current in the coil of conductive wire located nearby; the characteristics of this electric current are similar to those of the sound produced. At the other end of the line, a similar (but reversed) device, the loudspeaker, reproduces the sound wave.
Early communications have a fairly short range, with the voice rapidly weakening as the signal travels along the wire. First, expensive and moderately efficient relays are installed. They were replaced in 1906 by the first amplifiers (the triode of the American Lee de Forest): the extension of the network seems to have no limits. Today, the telephone network continues to expand. Where the cable network is insufficient (between continents or in the most isolated places), the telephone can also use telecommunications satellites, or even certain radio waves.
The first telephone connections through the Internet network saw the light of day in the early 2000s. On these telephone networks called IP networks (Internet Protocol, networks using the Internet Protocol; we also speak of IP telephony or VoIP for Voice over IP), the voice is digitized, compressed and then split into packets which pass over the Internet before reaching the landline or mobile of the recipient.
Mobility and the invention of the smartphone
Along with the development of the services offered by the landline telephone, the beginning of the 21st century saw the advent of mobile telephony. A mobile phone is a device where the connection wires to the telephone exchange have been replaced by a radio link. This kind of phone can in theory be used anywhere: in the car, on the train, on foot, etc. Radio stations connected to the conventional network are deployed throughout the country for this purpose, each covering a small geographical area called a cell. Because of this, cell phones do not need a lot of power, which allows them to be miniaturized as a handset with an antenna and all the necessary devices. Each signal is transmitted on a carrier frequency corresponding to the cell in which the user is located at that time. Narrowband frequency modulation is the most common transmission mode.
The ancestor of the mobile phone is certainly the car phone, heavy and bulky, which equips high-end vehicles of the 1960s. The year 1992 was a turning point in this field with the adoption in France and in the world of Standard GSM (Global System for Mobile Communications) using a digital signal. The mobile phone was democratized at the end of the 1990s to become an essential device in the majority of households. In 2008, there were more than three billion users, for a use mainly consisting of voice communications and messages (SMS).
The smartphone, a mobile phone with a touchscreen, has since been a huge success. Always more efficient and equipped with many features, it is a real small computer that allows multiple uses, from internet browsing to photography, including GPS guidance and games.
- Alexander Graham Bell, inventor of the telephone, by Michael Webb. Editions de la Chenelière, 1993.
- And Bell invented the telephone, Orlando John Stevenson. France-Empire editions, 1964.
- The fabulous history of inventions - From mastery of fire to immortality. Dunod, 2018.
- History of telecommunications in France, by Catherine Bertho. Eres, 1984.