The discovery of the telephone
Telephone Instrument for communicating by
voice over long distances were invented by
The Microphone Primary is a component in a sound-reproducing system, whereby the mechanical energy of sound waves is converted into electrical signals by means of a transducer. One of the simplest is the telephone receiver mouthpiece, invented by Scottish-US inventor Alexander Graham Bell in 1876; other types of microphone are used with broadcasting and sound-film apparatus.
Telephones have a carbon microphone, which reproduces only a narrow range of frequencies. For live music, a moving-coil microphone is often used. In it, a diaphragm that vibrates with sound waves moves a coil through a magnetic field, thus generating an electric current. The ribbon microphone combines the diaphragm and coil. The condenser microphone is most commonly used in recording and works by a capacitor.
Telecommunications and Communications over a distance is generally made by electronic means.
Long-distance voice communication was pioneered 1876 by Scottish
scientist Alexander Graham Bell when he invented the telephone. Today it is
possible to communicate with most countries by telephone cable, or by satellite
or microwave link, with over 100,000 simultaneous conversations and several
television channels being carried by the latest satellites. Integrated-Services
Digital Network (ISDN) makes videophones and high-quality fax possible; the
world's first large-scale center of ISDN began operating in
The first mechanical telecomunications
systems were the semaphore and heliograph (using flashes of sunlight), invented
in the mid-19th century, but the forerunner of the present telecommunications
age was the electric telegraph. The earliest practicable telegraph instrument
was invented by William Cooke and Charles Wheatstone in
The drawback to long-distance voice
communication via microwave radio transmission is that the transmissions follow
a straight line from tower to tower, so that over the sea the system becomes
impracticable. A solution was put forward 1945 by the science-fiction writer
Arthur C Clarke, when he proposed a system of communications satellites in an
orbit 35,900 km/22,300 mi above the equator, where they would circle the Earth
in exactly 24 hours, and thus appear fixed in the sky. Such a system is now in
operation internationally, by Intelsat . The
satellites are called geostationary satellites (syncoms). The first to be
successfully launched, by Delta rocket from
telecommunications Satellite dish. Geostationary communications satellites over the Earth's equator which orbit in 24 hours permit connections between all points on the Earth's surface to be made using such dishes. Satellite dishes are commonly used by European households to receive television channels broadcast by satellite.
Ultimele referate adaugate
- Mihai beniuc - „poezii"
- Mihai eminescu - student la berlin
- Mircea Eliade - Mioara Nazdravana (mioriţa)
- Chirita in provintie de Vasile Alecsandri -expunerea subiectului
- Dragoste de viata de Jack London
|Ion Luca Caragiale
- Triumful talentului… (reproducere) de Ion Luca Caragiale
- Fantasticul in proza lui Mircea Eliade - La tiganci
- „Personalitate creatoare” si „figura a spiritului creator” eminescian
- Enigma Otiliei de George Calinescu - geneza, subiectul si tema romanului
- Arta literara in romanul Ion, - Liviu Rebreanu