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IV TelecommunicationsTelecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages such as coded drumbeats, lung-blown horns, and loud whistles. In modern times, telecommunications involves the use of electrical devices such as the telegraph, telephone, and teleprinter, as well as the use of radio and microwave communications, as well as fiber optics and their associated electronics, plus the use of the orbiting satellites and the Internet. A revolution in wireless telecommunications began in the 1900s (decade) with pioneering developments in wireless radio communications by Nikola Tesla and Guglielmo Marconi. Telecommunication systemsA number of key concepts reoccur throughout the literature on modern telecommunication systems. Some of these concepts are discussed below. Basic elements A basic telecommunication system consists of three primary units that are always present in some form:
For example, in a radio broadcasting station the station's large power amplifier is the transmitter; and the broadcasting antenna is the interface between the power amplifier and the "free space channel". The free space channel is the transmission medium; and the receiver's antenna is the interface between the free space channel and the receiver. Next, the radio receiver is the destination of the radio signal, and this is where it is converted from electricity to sound for people to listen to. Sometimes, telecommunication systems are "duplex" (two-way systems) with a single box of electronics working as both a transmitter and a receiver, or a transceiver. For example, a cellular telephone is a transceiver.[26] The transmission electronics and the receiver electronics in a transceiver are actually quite independent of each other. This can be readily explained by the fact that radio transmitters contain power amplifiers that operate with electrical powers measured in the watts or kilowatts, but radio receivers deal with radio powers that are measured in the microwatts or nanowatts. Hence, transceivers have to be carefully designed and built to isolate their high-power circuitry and their low-power circuitry from each other. Telecommunication over telephone lines is called point-to-point communication because it is between one transmitter and one receiver. Telecommunication through radio broadcasts is called broadcast communication because it is between one powerful transmitter and numerous low-power but sensitive radio receivers.[26] Telecommunications in which multiple transmitters and multiple receivers have been designed to cooperate and to share the same physical channel are called multiplex systems. Mayor components of telecommunication systems are:
SignalA signal as referred to in communication systems, signal processing, and electrical engineering "is a function that conveys information about the behavior or attributes of some phenomenon".[1] In the physical world, any quantity exhibiting variation in time or variation in space (such as an image) is potentially a signal that might provide information on the status of a physical system, or convey amessage between observers, among other possibilities.[2] The IEEE Transactions on Signal Processing elaborates upon the term "signal" as follows:[3] "The term 'signal' includes, among others, audio, video, speech, image, communication, geophysical, sonar, radar, medical and musical signals." Other examples of signals are the output of a thermocouple, which conveys temperature information, and the output of a pH meter which conveys acidity information.[1] Typically, signals often are provided by a sensor, and often the original form of a signal is converted to another form of energy using a transducer. For example, a microphone converts an acoustic signal to a voltage waveform, and a speaker does the reverse.[1] The formal study of the information content of signals is the field of information theory. The information in a signal usually is accompanied by noise. The term noise usually means an undesirable random disturbance, but often is extended to include unwanted signals conflicting with the desired signal (such as crosstalk). The prevention of noise is covered in part under the heading of signal integrity. The separation of desired signals from a background is the field of signal recovery,[4] one branch of which is estimation theory, a probabilistic approach to suppressing random disturbances. Engineering disciplines such as electrical engineering have led the way in the design, study, and implementation of systems involving transmission, storage, and manipulation of information. In the latter half of the 20th century, electrical engineering itself separated into several disciplines, specializing in the design and analysis of systems that manipulate physical signals; electronic engineering and computer engineering as examples; while design engineering developed to deal with functional design of man–machine interfaces.
Infrared light is used in industrial, scientific, and medical applications. Its uses include thermal efficiency analysis, environmental monitoring, industrial facility inspections, remote temperature sensing, short-ranged wireless communication, spectroscopy, and weather forecasting. Directory: forms forms -> Form a-122 File No. Retirement homes act, 2010 application under section 116 of the act forms -> Course overview forms -> Pre-matric scholarship for students belonging to the minority communities forms -> Cutting Greenhouse Gases Global warming forms -> Bowl game blarney: Why Sports Tourism Trumps Logic in the Quest for a true College Football Champion in the United States” Prepared for: Dr. Tom Hinch Reviewed by: Tim Enger 0845772 Due Date: December 10, 2005 Word Count: 6,677 forms -> Steven m. Glassman forms -> Teresa k. Blodgett forms -> Atlanta Falcons Internet Scavenger Hunt forms -> Registration information forms -> Chapter 8 seaman to admiral-21 (sta-21) program Download 7.78 Mb. Share with your friends:
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