Presentation on theme: "Telephone ИСТОРИЯ СОЗДАНИЯ ТЕЛЕФОНА Boris Djudnev, School 1173, Form 11g, Moscow Борис Дюднев, школа 1173, 11 класс Г, Москва."— Presentation transcript:
Telephone ИСТОРИЯ СОЗДАНИЯ ТЕЛЕФОНА Boris Djudnev, School 1173, Form 11g, Moscow Борис Дюднев, школа 1173, 11 класс Г, Москва
Telephones An elementary telephone system consists of two elements: For each subscriber, the system must contain the equipment necessary to convert sound to electrical signals and back. This equipment is called the "telephone" and allows users to speak and hear each other. Most telephones are in two parts: The handset is a handle containing the transmitter and receiver. The base contains a dial to initiate a call and a bell or other signaling device to notify the user of a telephone call from another user. Some telephones have more or fewer parts, and some don't have this kind of integrated handset. The system must connect the two or more telephones together. Historically, and still usually, this is by means of twisted pair wire, and usually via the worldwide telephone network or PSTN. A telephone handset A French rotary telephone
History Credit for inventing the electric telephone remains in dispute. Antonio Meucci, Johann Philipp Reis, Alexander Graham Bell and Elisha Gray, amongst others, have all been credited with the invention. The very early history of the telephone is a confusing morass of claim and counterclaim, which was not clarified by the huge mass of lawsuits which hoped to resolve the patent claims of individuals. The Bell and Edison patents, however were forensically victorious and commercially decisive. Alexander Graham Bell
Copy of the original phone of Graham Bell at the Musée des Arts et Métiers in Paris 1896 Telephone (Sweden) CR64 Candlestick Phone
Later history The history of additional inventions and improvements of the electrical telephone includes the carbon microphone (later replaced by the electret microphone now used in almost all telephone transmitters), the manual switchboard, the rotary dial, the automatic telephone exchange, the computerized telephone switch, Touch Tone® dialing (DTMF), and the digitization of sound using different coding techniques including pulse code modulation or PCM (which is also used for.WAV,.AIF files and compact discs). In 1926 Bell Labs and the British Post Office engineered the first two-way conversation across the Atlantic. The first commercial transatlantic telephone call was between New York City and London and occurred on January 7, 1927. The industry has divided into telephone equipment manufacturers and telephone network operators (telcos). Operating companies often hold a national monopoly. In the United States, the Bell System was vertically integrated. It fully or partially owned the telephone companies that provided service to about 80% of the telephones in the country and also owned Western Electric, which manufactured or purchased virtually all the equipment and supplies used by the local telephone companies. The Bell System divested itself of the local telephone companies in 1984 in order to settle an antitrust suit brought against it by the United States Department of Justice. Newer systems include IP telephony, ISDN, DSL, mobile cellular phone systems, cordless telephones, and the third generation cell phone systems that promise to include high-speed packet data transfer. Touch Tone® telephone The Ericofon was a very futuristic handset when it was introduce d in 1956.
Cordless telephone Cordless telephones, invented by Teri Pall in 1965, consist of a base unit that connects to the land-line system and also communicates with remote handsets by low power radio. This permits use of the handset from any location within range of the base. Because of the power required to transmit to the handset, the base station is powered with an electronic power supply. Thus, cordless phones typically do not function during power outages. Initially, cordless phones used the 1.7 MHz frequency range to communicate between base and handset. Because of quality and range problems, these units were soon superseded by systems that used frequency modulation (FM) at higher frequency ranges (49 MHz, 900 MHz, 2.4 GHz, and 5.8 GHz). The 2.4 GHz cordless phones can interfere with certain wireless LAN protocols (802.11b/g) due to the usage of the same frequencies. On the 2.4 GHz band, several "channels" are utilized in an attempt to guard against degradation in the quality of the voice signal due to crowding. The range of modern cordless phones is normally on the order of a few hundred meters. Cordless handset