A report on Telecommunications

Earth station at the satellite communication facility in Raisting, Bavaria, Germany
Visualization from the Opte Project of the various routes through a portion of the Internet
A replica of one of Chappe's semaphore towers
Optical fiber provides cheaper bandwidth for long-distance communication.
Digital television standards and their adoption worldwide
here
The OSI reference model

Transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems.

- Telecommunications
Earth station at the satellite communication facility in Raisting, Bavaria, Germany

49 related topics with Alpha

Overall
A variety of radio antennas on Sandia Peak near Albuquerque, New Mexico, US

Radio

11 links

A variety of radio antennas on Sandia Peak near Albuquerque, New Mexico, US
Radio communication. Information such as sound is converted by a transducer such as a microphone to an electrical signal, which modulates a radio wave produced by the transmitter. A receiver intercepts the radio wave and extracts the information-bearing modulation signal, which is converted back to a human usable form with another transducer such as a loudspeaker.
Comparison of AM and FM modulated radio waves
Frequency spectrum of a typical modulated AM or FM radio signal. It consists of a component C at the carrier wave frequency f_c with the information (modulation) contained in two narrow bands of frequencies called sidebands (SB) just above and below the carrier frequency.
Satellite television dish on a residence
Satellite phones, showing the large antennas needed to communicate with the satellite
Firefighter using walkie-talkie
VHF marine radio on a ship
Parabolic antennas of microwave relay links on tower in Australia
RFID tag from a DVD
Satellite Communications Center Dubna in Russia
Communications satellite belonging to Azerbaijan
Military air traffic controller on US Navy aircraft carrier monitors aircraft on radar screen
ASR-8 airport surveillance radar antenna. It rotates once every 4.8 seconds. The rectangular antenna on top is the secondary radar.
Rotating marine radar antenna on a ship
A personal navigation assistant GPS receiver in a car, which can give driving directions to a destination.
EPIRB emergency locator beacon on a ship
Wildlife officer tracking radio-tagged mountain lion
US Air Force MQ-1 Predator drone flown remotely by a pilot on the ground
Remote keyless entry fob for a car
Quadcopter, a popular remote-controlled toy
Television receiver

Radio is the technology of signaling and communicating using radio waves.

Different types of physical transmission media supporting communication channels

Communication channel

5 links

Different types of physical transmission media supporting communication channels

A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking.

Network Packet

Computer network

7 links

Set of computers sharing resources located on or provided by network nodes.

Set of computers sharing resources located on or provided by network nodes.

Network Packet
Common network topologies
A sample overlay network
Network links
Fiber optic cables are used to transmit light from one computer/network node to another
2007 map showing submarine optical fiber telecommunication cables around the world.
Computers are very often connected to networks using wireless links
An ATM network interface in the form of an accessory card. A lot of network interfaces are built-in.
A typical home or small office router showing the ADSL telephone line and Ethernet network cable connections
Firewalls
The TCP/IP model and its relation to common protocols used at different layers of the model.
Message flows between two devices (A-B) at the four layers of the TCP/IP model in the presence of a router (R). Red flows are effective communication paths, black paths are across the actual network links.
SONET & SDH
Asynchronous Transfer Mode
Routing calculates good paths through a network for information to take. For example, from node 1 to node 6 the best routes are likely to be 1-8-7-6, 1-8-10-6 or 1-9-10-6, as these are the shortest routes.
Partial map of the Internet, based on the January 15, 2005 data found on opte.org . Each line is drawn between two nodes, representing two IP addresses. The length of the lines is indicative of the delay between those two nodes. This graph represents less than 30% of the Class C networks reachable.

Computer networking may be considered a branch of computer science, computer engineering, and telecommunications, since it relies on the theoretical and practical application of the related disciplines.

Multiple low data rate signals are multiplexed over a single high data rate link, then demultiplexed at the other end

Multiplexing

3 links

Multiple low data rate signals are multiplexed over a single high data rate link, then demultiplexed at the other end
Frequency-division multiplexing (FDM): The spectrum of each input signal is shifted to a distinct frequency range.
One stream, one color, light waves, in WDM.
Time-division multiplexing (TDM).
Telecommunication multiplexing

In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium.

The frequency spectrum of a typical radio signal from an AM or FM radio transmitter. The horizontal axis is frequency; the vertical axis is signal amplitude or power. It consists of a signal (C) at the carrier wave frequency fC, with the modulation contained in narrow frequency bands called sidebands (SB) just above and below the carrier.

Carrier wave

6 links

The frequency spectrum of a typical radio signal from an AM or FM radio transmitter. The horizontal axis is frequency; the vertical axis is signal amplitude or power. It consists of a signal (C) at the carrier wave frequency fC, with the modulation contained in narrow frequency bands called sidebands (SB) just above and below the carrier.

In telecommunications, a carrier wave, carrier signal, or just carrier, is a waveform (usually sinusoidal) that is modulated (modified) with an information-bearing signal for the purpose of conveying information.

Categorization for signal modulation based on data and carrier types

Modulation

6 links

Categorization for signal modulation based on data and carrier types
A low-frequency message signal (top) may be carried by an AM or FM radio wave.
Waterfall plot of a 146.52 MHz radio carrier, with amplitude modulation by a 1,000 Hz sinusoid. Two strong sidebands at + and - 1 kHz from the carrier frequency are shown.
A carrier, frequency modulated by a 1,000 Hz sinusoid. The modulation index has been adjusted to around 2.4, so the carrier frequency has small amplitude. Several strong sidebands are apparent; in principle an infinite number are produced in FM but the higher-order sidebands are of negligible magnitude.
Schematic of 4 baud, 8 bit/s data link containing arbitrarily chosen values

In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a separate signal called the modulation signal that typically contains information to be transmitted.

Cooke and Wheatstone's five-needle telegraph from 1837

Electrical telegraph

3 links

Point-to-point text messaging system, used from the 1840s until the late 20th century when it was slowly replaced by other telecommunication systems.

Point-to-point text messaging system, used from the 1840s until the late 20th century when it was slowly replaced by other telecommunication systems.

Cooke and Wheatstone's five-needle telegraph from 1837
Morse Telegraph
Hughes telegraph, an early (1855) teleprinter built by Siemens and Halske
Sömmering's electric telegraph in 1809
Revolving alphanumeric dial created by Francis Ronalds as part of his electric telegraph (1816)
Pavel Schilling, an early pioneer of electrical telegraphy
Diagram of alphabet used in a 5-needle Cooke and Wheatstone Telegraph, indicating the letter G
Morse key and sounder
GWR Cooke and Wheatstone double needle telegraph instrument
A magneto-powered Wheatstone A. B. C. telegraph with the horizontal "communicator" dial, the inclined "indicator" dial and crank handle for the magneto that generated the electrical signal.
Professor Morse sending the message – WHAT HATH GOD WROUGHT on 24 May 1844
Foy–Breguet telegraph displaying the letter "Q"
Wheatstone automated telegraph network equipment
A Baudot keyboard, 1884
Phelps' Electro-motor Printing Telegraph from circa 1880, the last and most advanced telegraphy mechanism designed by George May Phelps
A Creed Model 7 teleprinter in 1930
Teletype Model 33 ASR (Automatic Send and Receive)
Major telegraph lines in 1891
The Eastern Telegraph Company network in 1901
German Lorenz SZ42 teleprinter attachment (left) and Lorenz military teleprinter (right) at The National Museum of Computing on Bletchley Park, England

It was the first electrical telecommunications system and the most widely used of a number of early messaging systems called telegraphs, that were devised to communicate text messages more rapidly than by physical transportation. Prior to the electric telegraph, semaphore systems were used, including beacons, smoke signals, flag semaphore, and optical telegraphs for visual signals to communicate over distances of land.

Commercial FM broadcasting transmitter at radio station WDET-FM, Wayne State University, Detroit, USA. It broadcasts at 101.9 MHz with a radiated power of 48 kW.

Transmitter

5 links

Commercial FM broadcasting transmitter at radio station WDET-FM, Wayne State University, Detroit, USA. It broadcasts at 101.9 MHz with a radiated power of 48 kW.
A radio transmitter is usually part of a radio communication system which uses electromagnetic waves (radio waves) to transport information (in this case sound) over a distance.
Animation of a half-wave dipole antenna transmitting radio waves, showing the electric field lines. The antenna in the center is two vertical metal rods, with an alternating current applied at its center from a radio transmitter (not shown). The voltage charges the two sides of the antenna alternately positive (+) and negative (−) . Loops of electric field (black lines) leave the antenna and travel away at the speed of light; these are the radio waves. This animation shows the action slowed enormously
Hertz discovering radio waves in 1887 with his first primitive radio transmitter (background).
Guglielmo Marconi's spark gap transmitter, with which he performed the first experiments in practical Morse code radiotelegraphy communication in 1895-1897
High power spark gap radiotelegraphy transmitter in Australia around 1910.
1 MW US Navy Poulsen arc transmitter which generated continuous waves using an electric arc in a magnetic field, a technology used for a brief period from 1903 until vacuum tubes took over in the 20s
An Alexanderson alternator, a huge rotating machine used as a radio transmitter at very low frequency from about 1910 until World War 2
One of the first vacuum tube AM radio transmitters, built by Lee De Forest in 1914. The early Audion (triode) tube is visible at right.
One of the BBC's first broadcast transmitters, early 1920s, London. The 4 triode tubes, connected in parallel to form an oscillator, each produced around 4 kilowatts with 12 thousand volts on their anodes.
Armstrong's first experimental FM broadcast transmitter W2XDG, in the Empire State Building, New York City, used for secret tests 1934–1935. It transmitted on 41 MHz at a power of 2 kW.
Transmitter assembly of a 20 kW, 9.375 GHz air traffic control radar, 1947. The magnetron tube mounted between two magnets (right) produces microwaves which pass from the aperture (left) into a waveguide which conducts them to the dish antenna.

In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna.

The atmospheric attenuation of microwaves in dry air with a precipitable water vapor level of 0.001 mm. The downward spikes in the graph corresponds to frequencies at which microwaves are absorbed more strongly, such as by oxygen molecules.

Microwave transmission

3 links

Transmission of information by electromagnetic waves with wavelengths in the microwave range of the electromagnetic spectrum.

Transmission of information by electromagnetic waves with wavelengths in the microwave range of the electromagnetic spectrum.

The atmospheric attenuation of microwaves in dry air with a precipitable water vapor level of 0.001 mm. The downward spikes in the graph corresponds to frequencies at which microwaves are absorbed more strongly, such as by oxygen molecules.
A parabolic satellite antenna for Erdfunkstelle Raisting, based in Raisting, Bavaria, Germany
C-band horn-reflector antennas on the roof of a telephone switching center in Seattle, Washington, part of the U.S. AT&T Long Lines microwave relay network
Dozens of microwave dishes on the Heinrich-Hertz-Turm in Hamburg, Germany
Communications tower on Frazier Mountain, Southern California with microwave relay dishes
Danish military radio relay node
Production truck used for remote broadcasts by television news has a microwave dish on a retractible telescoping mast to transmit live video back to the studio.
Antennas of 1931 experimental 1.7 GHz microwave relay link across the English Channel. The receiving antenna (background, right) was located behind the transmitting antenna to avoid interference.
US Army Signal Corps portable microwave relay station, 1945. Microwave relay systems were first developed in World War II for secure military communication.
Richtfunkstelle Berlin-Frohnau
Microwave spying

Although an experimental 40 mi microwave telecommunication link across the English Channel was demonstrated in 1931, the development of radar in World War II provided the technology for practical exploitation of microwave communication.

Data communication

6 links

Transfer and reception of data in the form of a digital bitstream or a digitized analog signal over a point-to-point or point-to-multipoint communication channel.

Transfer and reception of data in the form of a digital bitstream or a digitized analog signal over a point-to-point or point-to-multipoint communication channel.

Digital transmission or data transmission traditionally belongs to telecommunications and electrical engineering.