History of telecommunications


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Terminology electricity and telecommunications








Commutazione di circuito (Circuit Switching)
Commutazione di pacchetto (Packet Switching) LAN
CONDUTTORE Larghezza di banda


Modello di riferimento OSI















E-conference REOSTATO
E-learning RISONANZA



Asymmetric Digital Subscriber Line.  One of the four DSL technologies.  ADSL transmits width of Banda broader currently receiving and in the transmission.  Receive data moving between 1.5 and 20 Mbps, transmission between 16 Kbps and 20 Mbps.  ADSL covers distances up to 5500 metres on single pair copper telephone from the central telephone.
 Asynchronous Transfer Mode.  Modes of transport asynchronous transferring multiple traffic (such as voice, video or data) in the cells of fixed length of 53 bytes (rather than in "packages" of variable length in technologies like Ethernet and FDDI).  ATM mode allows you to reach high speeds and becomes particularly widespread in the backbone network traffic.  The network equipment next generation can support transmission in ATM WAN, making it interesting even for large organizations geographically distributed
(A/m):(V / m) means the unit of measure in the International System of magnetic field intensity (H). 1 A/m    1 A / m corresponds to a magnetic field produced by a current of 1 A linear distance of 1/2p m.

Magnitude: the scale is the value assumed moment to moment components of a wave, in the case of an electromagnetic wave it is the instantaneous value of the electric field (measured in V / m) and / or magnetic field (measured A / m). (You see ELECTROMAGNETIC WAVE)
An analog signal is a signal electric or electromagnetic wave which can be transmitted through cables (coaxial, telephone) or the air.  It is characterized by three sizes: amplitude, frequency and phase.

ANTENNA Operative act to capture or radiate electromagnetic waves

ABSORPTION ELECTROMAGNETIC THE HUMAN: the human body exposed to a field

Absorbing electromagnetic energy.  The extent of energy depends on the wave frequency electromagnetic incident, as well as the shape and size of the body exposed to the wave front.
The absorption presents a maximum at a frequency (resonance frequency), which is linked to the size of the body. At frequencies less than that of resonance absorption decreases rapidly, while at higher frequencies initially and then decreases to a value remains nearly constant.  For a man of average size of the resonance frequency is around 70 MHz, while shares of the exposed body of a smaller size, the resonance frequency is higher, up to frequencies of the hundreds of MHz, for example to the retina is a resonance frequency of about 21 Ghz for the crystal about 9 GHz, etc.  The electromagnetic energy absorbed by a biological tissue is converted into thermal energy (heat), as the electromagnetic field it oscillation charges and molecular dipoles in the field, and these oscillations, through the interaction between the molecules are degraded in disordered molecular motions, that is precisely heat.  One of the most important molecules pri absorbiranju electromagnetic energy is water, which is a permanent molecular dipole (see DIPOLO ELECTRIC). See also MECHANISMS OF ADJUSTMENT AND DISPERSION OF HEAT.
When changes the circulating current in a conductor, the variable magnetic field resulting invests the same conductor leading to it unlike potential.  This difference in potential car induced opposes the applied potential difference and tends to limit or reverse the original current. The concept of auto power is similar to mechanical inertia.  A coil of arrest tends to sweeten the current trend of a variable, as a fly sweetens the rotation of an engine. The ability to avtoindukcije a coin is quantified dall'induttanza, which is independent of the intensity of current or potential difference and is determined solely by the geometric characteristics of the coil and magnetic properties of the substance that forms the nucleus.
Synthetic resin insoluble, used to manufacture paint, insulation materials, various objects.  It takes its name from its inventor Baekeland.
It is the unit of measurement for speed transmission of data over the network.  Indicates the number of discrete elements that can be transmitted per second.  Each baud can be a bit different as bits, 1 baud is 1 bps if it is just a bit 1. . Baud odgovornega name derives from the French Emile Baudot (1845-1903).
 Indicates the width of Banda network that is the ability to convey with a single means different signals at the same time. Generalmente impiega cavi coassiali. Generally uses coaxial cables.  Also called "Wideband".
BROADCAST The literal translation means "big ring" and in radio and television this word is used with the meaning of "spreading forward to wide-ranging" general interest news and entertainment.

ELECTRICAL FIELD: electric field can define a region of space in which an electrical charge (or body electrically load) is subjected to a force proportional to the office. To describe the camp uses the electric field vector, which indicates that represents E and the electrical force acting on the charge.  In the International System unit of electric field is the newton / coulomb (N / C) or volts / m (V / m) or their multiples (for example kV / m).  The electric field is generated by electric charges, or even by a magnetic field varies over time (See LAW OF FARADAY).  When electric charges that generate an electric field are fixed in space the electric field has a constant value at any point and is called electrostatic field.
ELECTROMAGNETIC FIELD: a magnetic field variable frequency f, produces near a variable electric field, which is also the frequency f, which still gives rise close to a magnetic field… variable, and so on. Magnetic and electric fields quickly variables not remain between them separated: one giving rise to another and coexist in both inseparable entity which is called electromagnetic field. As a result of the process of mutual generation, under appropriate conditions, the electromagnetic field propagates in that it away from its source, with a characteristic speed, which in a vacuum coincides with the speed of light (c '3,108 m / s) generating so that the electromagnetic wave.
MAGNETIC FIELD: The magnetic field is generated by moving offices, from current
elettriche, ea sua volta agisce su correnti, ovvero cariche in movimento. Electrical, and in turn acts on current or offices on the move. The magnetic field can be created by an electric field varies over time (see equations OF MAXWELL).  The permanent magnets (magnets) generate a magnetic field caused by the presence of current, said current atomic due to the motion of electrons (spin). The magnetic field is represented by a vector called magnetic induction B or H said intensity of magnetic field. The relationship between H and B is as follows: H = B / m and m = magnetic permeability of the medium in question. Graphically the magnetic field is often represented by the lines of force that are in bribes every point to the direction of magnetic field vector (either B or H), in agreement with Farady, the number of lines of force perpendicular crossing the unit area is proportional to the carrier. See also FLOW MAGNETIC. 

ELECTRIC CHARGED: the electric charge should be considered a fundamental properties of matter.
 There are two types of electric charge, one positive and one negative. Two electric charges of the same type are rejected, two opposite charges attract each type.  The unit charge in the International System is the coulomb (C), which is defined as the amount of power flowing in a second when a current stationary 1 amp.  There is naturally a basic minimum electric charge, which corresponds to that of (e = 1.6 × 10-19 coulombs) and any other office is always a multiple of this.

The digital certificate, also known as Digital ID is the electronic equivalent of a
passport or a trade licence. It is issued by an independent Certificativa = Certification Authority (CA) and officially certify the identity of its owner.  A Digital ID is composed of two complementary keys.  It is a dual system-key: a private key is installed on the server of the company that sells to the public products or services and can be used exclusively by the Company, a public key is distributed and incorporated in all browsers, such as Internet Explorer and Netscape Navigator, by the Certification Authority.
We need to avoid interference in the reception, due to  Presence of multiple transmitters in the same area, which  Emit signals on frequencies not well defined, not precisely tuned. With these circuits patented by the Marconi  1900 for the avoidance of interference, the receiver equipment can  Be tuned precisely through a tuner, Wavelength of the station you want to receive.
COHERER tool developed by physicists dell'800 (Themistocles  Calzecchi Onesti in Italy, Désiré-Edouard Branly in Eugène France, Oliver Joseph Lodge in England), which had shown a sensitive detector of electromagnetic waves. It consisted of a small glass tube filled with metal filings (Nickel and silver), which became conductive power when it was hit by waves electromagnetic,                              
Switching circuit (Circuit Switching)
In a network to "circuit switching", when a session is open communication, a contact is established between the caller and call.  The telephone network PSTN, which is of this kind, ensures the quality of service (QoS) to conversation dedicating a full-duplex circuit with a width of 64 KHz Banda. The width of Banda remains unchanged regardless of whether the parties are in active conversation or silence. The technology "circuit switching" the ability of the channel transmission is entirely devoted to a single type of transmission. For this reason we can not use this line for phone and surf the Internet simultaneously. To do both is available alternative technologies (eg. ISDN and ADSL).

Packet switching  Technology transfer files on which is based the development of the Internet. Every single message is divided into "packets" of data from fixed size, with its identification number, the address of the sender and recipient.  All this information is contained in the package. The "package" of data can thus travel in the network independently using the quickest way to reach the goal. This technology makes it possible to use the same communication channel for getting the same packages containing different data.  Upon arrival at their destination, the message is reassembled in its original form. Il "packet switching" è stato elaborato da Paul Baran negli anni '60. The "packet switching" has been drawn up by Paul Baran in the 60's. 
CONDUCTOR ELECTRIC  means any body or means capable of conducting current electricity.
ELECTRIC POWER AC: it is called an alternating current electrical current which sinusoidalmente intensity varies as a function of time.  For the distribution of electricity usually uses alternating current frequency of 50 Hz (in Europe) or 60 Hz (USA).
ELECTRIC POWER CONTINUES: an electric current is called continuous if its intensity and its direction (conventionally understood as a move towards virtual positive charges), do not vary over time.
ELECTRIC POWER: it is called electricity each ordered motion of electric charges.  The intensity of the electric current is expressed by the amount of power (in coulombs, C), which crosses a certain section in time (seconds, s).  The current intensity in the International System, as the unit of measure the amp (A). 1 ampère corrisponde ad 1 coulomb/s. 1 corresponds to 1 amp coulomb / s.

ELECTROMAGNETIC FIELDS BUTTONS (PEMF): an electromagnetic field which varies cyclically with a period T, whose intensity is greater than a certain value (which may be zero) for a period of time less than T.   

 CURRENT INDUCED the induced current is a trend that manifested in a driver every time that this is placed in a region of space where there is a magnetic field varies with time. According to Faraday's law (one of four Maxwell equations) during the remains fintantoché you is a variation of the magnetic field flux and is both how much faster is the variation. On Faraday's law based on many applications, such as alternators and dynamo, which, in power stations, generating electrical energy into mechanical energy starting (rotation of an engine produced Thermal or the fall of the water).
POWER INDUCED the induced current is a current that occurs in a conductor whenever this is a region of space where there is a magnetic field varies over time.  Under the law Faraday (one of four equations Maxwell) remains current as long as there is a change in the flow of magnetic field and is greater as soon as is the variation.  The law is based Faraday many applications, such as alternators and dynamo, allowing, in power stations to generate electricity from mechanical energy (the rotation produced by a heat engine or fall of water).

Dielectric constant ABSOLUTE (OR CONSTANT DIELETTRICA) and is a parameter characteristic of a material and is the barrier effect that the material itself produces two posts when immersed in it interact: the strength of interaction (Coulomb force) is reduced by factor and .It is the characteristic of insulation material.  The dielectric constant absolute vacuum system e0 apply international 8.85 × 10-12 (C2 / N) m2. Usually a substance has a dielectric constant and greater than 0 and; The report e/e0 = er is the so-called relative dielectric constant. Er depends on the frequency and electromagnetic field applies: This frequency dependence is the so-called dielectric dispersion.
DENSITY OF POWER: The current density in a point is defined by the relationship between the intensity of current through a surface (perpendicular to the direction of current) and the surface of the same.The current density is a carrier and indicates J. It shows that the intensity of current can be represented as the flow of carrier J through the section of the conductor. The current density in the International System, is measured in ampère/metro2 (A/m2).We often use the submultiples: milliampère/metro2 (mA/m2) microampère/metro2 (mA/m2) or microampère / cm 2 (mA/cm2); sometimes uses the nanoampère/metro2 (nA/m2).
DIELECTRIC: it is not a material or conductor insulation.  In these substances do not have offices  Free electricity, namely the electrons are closely associated with atoms and can not be removed from their home by an ordinary electric field.
A digital signal is a sequence of pulses that can be sent through a cable or wireless devices.  The digital data can be represented directly in the form binary or Using appropriate instruments, as analog signals. It provides for the use of discrete signals (set at levels) to represent data such as text, images, sounds, video, etc. ..Digitizing a sound means of taking samples (sampling) by measuring the intensity at regular intervals of time.

Domain Name System. Not a real Internet protocol, but rather a system to translate the names of nodes (eg www.nasa.org) numeric addresses (eg

 Alphabetical name that identifies an Internet server to which is tied a numeric IP address used For data transfer, translation is entrusted to the DNS.  The domain name is divided into several parts: the top-level domain (Top Level Domain), the right URL, which often identifies the nation domain (example: it = italy, uk = england, france = fr ...) or its qualifying (com = commercial org = organization mil = military edu = university ...). In the OSI standard is called Country Code, the PRMD (Private Domain) name, generally the middle of the URL, such as "rai" www.rai.it.  Called often second-level domain, the subdomain is the most left of the URL.  The top-level domain must be applied to a specific body differently for each nation. 

Affectionately known as "backbone".  It is the part of the network that is a main route for traffic (for example, between subnets). We talk about backbone for data transmission along a country or a continent.

Digital Subscriber Line.  Technology network that broadcasts with a width of a large distances  Limited and through traditional copper telephone pair. Le DSL sono di quattro tipi: ADSL, HDSL, SDSL e VDSL. The DSL are of four types: ADSL, HDSL, SDSL and VDSL.  Each of them uses two specific devices (similar to modems) at either end of the transmission. Since most of DSL technology does not use all the available bandwidth on the pair, remains "space" for a voice channel (for example for normal phone calls). Vedere anche ADSL, HDSL, SDSL e VDSL. See also ADSL, HDSL, SDSL and VDSL. 
DVD Digital Video Disc.

Digital Video Disc.  Support on which you can record data on both sides, on two levels. Similar to CD-ROM can be writable (DVD-RAM with a capacity of 2.5 GB per side), not writable (DVD-ROM with a capacity of 3.9 GB per side) and prerecorded (DVD with a capacity of 17 GB on double-sided and double-level). 
Electronic Business. Automated Monitoring of all business processes through which you can constantly monitor all kinds of activity (buy, sell, provide online assistance, see lists and catalogs on the network, etc..).The term was introduced for the first time in 1997 by IBM.  Currently, more organizations are reviewing their business processes on the basis of future developments of the Internet and potential of the new means of communication.
Electronic Commerce.
The "electronic commerce", or the ability to buy products and services on-line through the World Wide Web and pay by credit card or receipt of the goods.  E-commerce is actually a strategic tool which enables companies to get more revenue with the expansion of its market, with the loyalty of its customers, by lowering the costs and greater efficiency. Sites electronic successful business are generally those businesses faster in understanding and exploiting Internet technology constantly evolving to gain competitive advantages.
Electronic Conference.  That is, "electronic conferences. Si discute in forma scritta via computer. It discusses in writing via computer. It is a dual system be activated from anywhere company.
Electronic Learning. Training based electronic procedures. Educating students on line, it was able to distribute information and training using multiple media simultaneously, and managing the learning process along the entire chain from which winds up a headquarters to remote instructors and experts. The company, in this way, can reuse and reset the contents of information with speed and ease, significantly reducing the development time and distribution of a high value-added
Electronic Mail. Posta elettronica, ovvero scambio di messaggi e di file attraverso una rete locale o Internet. E-mail or exchange of messages and files through a local network or the Internet. Avviene in tempo reale ed è indipendente dalla posizione fisica dei computer mittente e destinatario. It happens in real time and is independent of the physical location of computer sender and recipient. I messaggi e file vengono conservati da un server di tipo POP e/o IMAP che provvede ad inoltrarli al destinatario quando questo si collega. Messages and files are maintained by a server type of POP and / or IMAP that can forward them to the recipient when it connects.
PIEZOELECTRIC EFFECT: is the appearance of electric charges to the contrary faces Some crystals subjected to mechanical deformation along certain directions and vice versa (dual effect): the polarization of a material through an electric field it produces a mechanical deformation.  This effect has great practical importance, for example, is used in the construction of oscillators that produce ultrasound, or to convert mechanical oscillations in electrical fluctuations. Certain biological tissues such as bones have piezoelectric properties.
Electric  to  Greek ELEKTRON = AMBRA
Electricity term introduced in 1694 by R. Boyle scientific terminology.
Electrolysis chemical decomposition using electricity, a term coined by Faraday
Electromagnetism term coined by Oersted
ELETTRONVOLT (eV): units of measurement for energy used in physics to measure energy  Atomic Energy. A elettronvolt (eV) is the energy acquired by an electron that passes through Unlike potential of a volt.  Because the International System and Office of = = 1.6x10-19 C  . Then follows that 1 eV = 1.6x10-19x1V = 1.6x10-19 J.

ENERGY: Energy can be defined as the ability of a body to do work, and the extent of this work is also far.  There are different forms of energy: a body that moves has called kinetic energy.  Even a firm body can have energy, due to its position that potential energy. In addition, every body has an energy related internal energy of its atomic components. Still, the law of Einstein E = mc2 (with mass m = c = speed of light = 3x108m / s) provides that each mass is associated energy, and virtually vice versa.  Although we are accustomed to think of energy as an attribute of a body, it can exist even without the presence of a material body (ie having mass). For example an electromagnetic field has energy, electromagnetic energy that, even where there is no issue. L’energia è una grandezza scalare ed ha come unità di misura nel Sistema Internazionale il joule (simbolo J). Energy is a size and scale as the unit of measurement in the International System joule (J symbol).
The most popular LAN technology invented by Xerox Corporation and subsequently developed by the Xerox along with Intel and Digital Equipment Corporation.  The technology uses the protocol Ethernet CSMA / CS (Collision Detection) to move packets between computers.  Opera on various types of cables (coaxial or telephone doppini) at a speed of 10 Mbps, is similar to the IEEE 802.3 standard series. Vedere anche 10Base2, 10Base5, 10BaseF, 10BaseT e Fast Ethernet. See also 10Base2, 10Base5, 10BaseF, 10BaseT and Fast Ethernet. 

EXTRANET    A network like the Internet but limited access to partners, suppliers or customers of a company, which is It allows to share a simple and cost information and resources.

 The fiber optic cable uses light signals to transfer data and transmit them through thin Fiber glass. It is generally made up of a central glass surrounded by several layers of protective materials.  The fact that transmit light pulses instead of electrical signals to eliminate the problem of electrical interference. That is why the media is ideal for those environments that have several electrical interference.  The data that travel on optical fibers are transferred at high speeds and over longer distances compared to coaxial cable and twisted pair.The optical fibers are often used for the backbone LAN (backbone). 

FIREWALL  The firewall (literally "fire wall") is a system that prevents unauthorized access.
This essentially is a system capable of controlling access to networks intercepting messages all inbound and outbound.. 
MAGNETIC FLOW: number of power lines that cross a given surface perpendicular by dividing the number of lines of strength for the surface you get the same density Magnetic flux.

Photonics  Science studying phenomena, techniques and systems based on the control of photons, that is based on the quantum nature of light. Or, scientific-technological sector on the design and production of devices and systems that the information is transported and processed by photons.

FRAME Group logical information sent as a unit level data link about half trasmissivo.Spesso coincides with the header information (header) that control synchronization errors and the sending of information contained in the customer. The terms cell, datagram, message, package and segment are also synonyms to describe logical groups of information sent to various levels of OSI model.
FRAME RELAY  Technology geographical link (WAN) packet switching that operates at the level
DATA CONNECTION.This protocol is more efficient for the X .25
Frequency: number of times a periodic phenomenon occurs in time, or number of
oscillazioni  nell’unità di tempo. Fluctuations in time.  in Typically, the frequency is measured in hertz (Hz) or in an equivalent manner,  Second-1 (s-1), which represents the number of oscillations (or courses) per second.

File Transfer Protocol. Part of the main group (TCP / IP) Internet protocol, which is used to transfer files from the Internet server computer customers.

SCALAR SIZE : greatness that is completely determined by the number measure to a certain scale. It 'a number that expresses a relationship between size and magnitude another of the same type used as a unit. For example, the length, time, temperature are sizesscalar; they can be defined with a number that expresses their measure.
SIZE VETTORIALE (OR CARRIER): size determined by a form (or intensity), which is the numerical value according to a scale set arbitrarily, and its direction. Graphically is a vector represents a segment directed by the length of which is the intensity of the carrier. Carriers are often marked with bold letters or letters soprassegnate by an arrow (for example ao).  A carrier may be added or subtracted to other carriers and can be multiplied for a magnitude scale for another carrier: nell'algebra vector there are two types of multiplication possible: the scalar product and the product vector (or product and Product external).
GSM Global System for Mobile Communications. Global System for Mobile Communications. Standard Committee (worldwide) for cellular mobile telephony.  Initially it was designed for use on Banda of 900 MHz, then expanded to 1,800 MHz frequencies. Being a digital system, GSM allows, in addition to voice transmission, the transmission of fax and data transmission up to 9,600 bps.
High-Data-Rate Digital Subscriber Line. One of the four DSL technologies.  The HDSL forward with Banda width equal to 1544 Mbps is currently receiving and transmission over twisted pair cable double. The HDSL covers distances up to 3658.5 meters.  See also ADSL, SDSL and VDSL.
HEAT: energy flowing from one body to another as a result of the temperature difference that there is between them.  We often measure calories but in the International System unit of measurement is the joule (J).  (See WORK).

HEAT SPECIFIC: heat capacity (See CAPACITY 'HEAT) of a homogeneous body per unit of mass, that is the amount of heat required to raise the temperature a degree of unit mass of a substance.  Each material (substance) has its characteristic specific heat that usually depends on the temperature and pressure of the same.

HyperText Markup Language.  Simple language for formatting documents used to prepare pages to be viewed by a Web browser.  Created in 1991, the HTML was subsequently developed by CERN in Geneva. This is a fairly simple language.  There are many versions of HTML, all, however, must pass the approval of the W3C, the organization that regulates and promotes the use of standards.  The operator uses the HTML is called "accatiemmellista". There are various HTML editors on the market that facilitate or fully automate the creation of HTML code, allowing layout documents without any knowledge of programming.
Hypertext Transfer Protocol.  Protocol which Basa on the WWW (World Wide Web). In principle the only activity performed by an HTTP server is to send files, whether textual documents, documents in HTML format, images, sounds, on the basis of requests received from clients of customers through Internet browsers.
Institute of Electrical and Electronics Engineers.  American Body issuing the IEEE. These specifications define the standards of various communication protocols and network.
ADDRESS IP address to 32 bits, assigned to hosts using TCP / IP, which uniquely identifies each computer connected to the network.  The IP address may belong to the class A, B, C, D or E, and is displayed as a sequence of 4 numbers separated by a decimal point, for example,  The customer, however, is accustomed to request viewing a page on the Internet with typing a URL, ie an alphabetical easy to store and not with the type of an IP address, which is obviously more difficult to remember.  However servers on the Internet use to communicate the IP address corresponding number entered at the Client. translation from URL to IP address is performed by DNS.
The set of all network connections.  Each network consists of a set of computers (nodes) between them connected by TCP / IP protocol. However, there are networks that are not based on TCP / IP and are therefore not regarded as belonging to the Internet, but may communicate with these networks through gateways. Internet can be considered the evolution of the ARPANET system.

Network similar to the Internet but limited access to only employees or members of the organization. This is usually used by companies for connecting the headquarters with the various branches around the world.  It is accessed via password.
Each point in space where there is a magnetic field is called a magnetic induction B carrier, whose amplitude is the maximum value of the power that is exercised on the current explorer divided by the product of current and for the same length of the item. This vector characterizes so complete all properties of magnetic field and is measured in the International System, tesla (symbol T) by the name of the physical Croatian Nicola Tesla.  Sometimes it's also used an old unit of measurement called gauss (G symbol, 1G = 10-4T). Vedi anche FLUSSO MAGNETICO. See also FLOW MAGNETIC. 

INTENSITY OF POWER (POWER): defines current intensity across a surface S on the amount of power that moves through time in the same area.  It is a greatness Climb and as the unit of measurement in the International System, the amp (A).   A 1 = coulombs / s, where  Coulomb (C) indicates the charging unit.
Internet Protocol. It is the communication protocol of the Internet.  The messages are divided into packets and sent over the Net.  The IP protocol with each package adds the necessary information (including the IP address of the target computer) so that every host / router can route the packet to the final destination
Integrated Services Digital Network.  Communications Protocol is used for telephone connections between computers and geographically distributed networks.  An ISDN line includes at least two channels for the transmission of data or voice (called B-channel, 64 Kbps) available to clients a more channel (called D-channel, 16 Kbps) service for the control signals.

International Standard Organization. Born in 1947 in London, this organization to voluntary participation presides over the regulation of international standards covering a wide range of sectors. In 1978 the ISO OSI propose a model reference levels for 7 systems network.
INSULANT ELECTRIC OR INSULANT: device high electrical resistance used to support or  separate conductors to prevent current flows between unwanted tenants themselves and other objects.
Local Area Network.  Network group or network segments confined in a building or campus, connecting computers and peripherals (eg printers, faxes, scanners) installed at the same venue (eg same building, in different levels) or in nearby locations (eg . two adjacent buildings). The LAN operate at high speed, for example Ethernet has a data transfer rate of 10 Mbps or 100 Mbps in the case of Fast Ethernet. Confrontare con la voce WAN. Comparing with the voice WAN.
Width Band
Specify the extension of the frequency spectrum used for the transfer of data.  Identify the maximum speed of data transfer that a signal can reach about half physical, without significant loss of power.  For example, a link GigaEthernet is able to transfer 1 billion data per second.
ELECTRICAL WORK: work done by an electric field to move an electrical charge from an A
a un punto B. To a point B.  The electrical work is the following expression: L = q (VA-VB) where VA and VB are
electrical potential of A and B respectively.
WORK: When a force acting on a body moves him for a certain distance is said that the force is the work is defined as the product climb between the carrier that represents the intensity  Of force and the displacement vector. The unit of work in the International System, is the joule (J).1J= 1N×m. 1J = m × 1N 

VISIBLE LIGHT: non-ionising radiation with frequencies from 385 × 106 × 750 MHz and 106 MHz
end wavelength between 0.4 and 0.8 mm.  (See SPECTRUM ELECTROMAGNETIC)
WAVELENGTH: is the maximum distance between two (or two minimum) of a sine wave. La The
lWavelength indicates with the letter l and as the unit of measurement meters (m).
Metropolitan Area Network. Network which stretches over underground. He then a geographic area larger than a LAN but smaller than a WAN. Vedi anche LAN e WAN. See also LAN and WAN.

MODEM Modulator-demodulator. Device that allows a device Data (eg. A computer) to connect to other data devices through traditional phone line.  Modems "modulate", ie converting digital signals of the data for analog transmission and them "demodulano" ie riconvertono them in a digital language, understandable  to apparate data at the other end of the phone line.

Program seeking documents on the basis of certain keywords entered by those who carry out research. Vi sono diversi tipi di motori di ricerca. There are different types of search engines. The ftp search, for example, allow you to check on the network all FTP sites that contain a certain file and let you get it.

Motion Picture Experts Group. Standard di compressione video. Standard video compression. MPEG1 is the standard for audio and video optimized for networks with bandwidth equal to 1.5 Mbps.  MPEG2 is used for audio applications and high-quality video travelling on networks with bandwidth between 4 and 9 Mbps.  MPEG4 is finally a compression algorithm for network connections at 64 Kbps.
WAVE ELECTROMAGNETIC: electromagnetic waves called electromagnetic fields that propagate through space, even in the absence of matter. The transverse electromagnetic waves are: the electric field vector E and the magnetic field vector H are mutually perpendicular and lie on a plane perpendicular to the carrier v, the wave propagation speed. The relationship between E and H, electromagnetic wave is determined by the Maxwell equations.  Like any type of wave, a wave electromagnetic energy can carry from one point to another and can be characterized by lasua frequency (or its wavelength) and its amplitude.

NETWORK  means network and, in the language of the mass media, means any combination of radio and television that they connect with one another on circuit to send joint programmes on national territory
Ohm unit measuring resistance that has the same name of its discoverer Ohm

OSI  Model OSI (Open Systems Interconnection).  All hardware and software system that revolves around networks is governed by well-defined rules that refer mostly to the so-called OSI model, made in 1984 by ISO (International Standard Organization). This model provides a standard for network interconnections of the various PC.

OSI Reference Model
The International Organization for Standards (ISO) has developed the OSI network model (Open System Interconnection), which is composed of seven levels (or layer) different.  Standard Levels and the interfaces between these different parts of a given protocol may be modified or replaced as technologies advance, or that the system requirements change. The 7 Levels of the OSI model are as follows: Level 1 °: Physicist; 2 ° Level: Connecting data; ° Level 3: Network; 4 ° Level: Transportation; 5 ° Level: Session; 6 ° Level: Presentation; 7 ° Level : Application. The IEEE 802.11 includes Level 1 - Physical (PHY - Physical Layer) and the lower level of connection data. The bottom level of connection data is often referred to as sublevel MAC (Medium Access Control). 

PACKAGE   Group data with a header , which may indicate the contents of the package and its recipient.  One can imagine a package as a "data envelope" with the header which acts as address.  Packets are sent to recipients through networks by using "packet switching".

PBX  Private Branch Exchange. It is a telephone system that allows you to make telephone conversations between customers inside the company and from / to external lines. This is the classic telephone switchboard technology that uses analog or digital.
PERIOD: the smallest interval of time after which a motorcycle magazine summarizes the same Physical characteristics (size and its derivative).The term refers to the symbol T and its units The second measure (s).
PERMEABILITA 'MAGNETIC m is a parameter characteristic of the material and is the ability to allow this to permeate by magnetic fields.  The magnetic permeability of vacuum m0 namely, the International System, 4p10-7 H / m. The report m/m0 = mr is the so-called relative magnetic permeability (empty). Mr is used to distinguish between substances diamagnetiche (mr <1) and substances  Paramagnetic (mr> 1).
Post Office Protocol. This is the first protocol-mail address. Il server POP immagazzina la The server stores the POP  Mail arrives and makes it available when the customer connects.  Since version POP3 is the reading of messages arrived that the composition of the new messages can be performed off-line. A protocol of this kind, but much more advanced, is the IMAP. POPs can be construed as "Point of Presence", ie as a point of access to the local network. 
A portal site is a very complex they are grouped by topic and information services,  as well as commercial publishing. Usually a portal contains at least one search engine, news flashes updated in real time, pages and deepening of various utility services for customers. 
POWER: is the ability to produce work per unit of time.  Also, energy Produced or loss per unit of time. In the International System unit of power is the J / s, said Watts (Symbol W)

POTENTIAL ELECTRIC: Is the work that must be done against the forces of the field to lead a charging unit from one point of reference to the point in question, the reference point is Indefinitely or for convenience, on the surface of the earth or some other major tenant. Il potenziale The potential Electric is a size and scale in the International System is measured in volts, the symbol V (1J = 1V / C).  The electric potential can be considered as a quantity as intensive pressure, or the level in a fluid. A difference of potential can lead a positive charge from a greater potential to one with less potential, similar to what the water that runs from a higher level to  Lower.
PRODUCT VETTORIALE between two carriers that a and b are tilted an angle q is written as: axb
and is defined as a carrier that has the form given by ab × senq direction perpendicular to the plane
Has to be given to and from the direction of progress of a screw dextrogyrate, prepared Perpendicular to the plane containing the two carriers, which go on through the corner b more small.
Formal description of a set of rules and conventions that govern the way in which network devices must exchange information.
The Proxy Server are servers that "filter" the information arriving from the Internet through the firewall. When you connect to a proxy with its client software, the server starts its client software (proxy) and provides the data. Since the proxy server duplicate all communications, are able to maintain logging of everything they do.   The advantage of proxy servers is that they are completely safe, if configured properly, failing to direct IP routes.

RADIO GALENA  The mineral is galena (lead sulfide).  It was used as a detector signals received from the antenne.

Radio   Communications through the transmission of radio waves between two or more stations. Basically a station transmitter is made up of a transmitter, which produces high signals Frequency, and it has an antenna fed, which radiates in Space modulated radio waves in such a way as to allow the transmission of information.
Radiofonia Transmission through radio waves of sound signals between two users a broadcasting station to multiple users  simultaneously (broadcasting).

Radioreceiver  Device capable of receiving radio waves that come from  a Stations transmitters, extract and amplify the signal,  Modular low frequency.
Sistema di telegrafia che fa uso di onde radio per trasmettere Telegraphy system that uses radio waves to transmit
messaggi secondo un codice prestabilito. Messages according to a predetermined code.

DETECTOR  Device a radio receiver, a deputy  signal the presence of electromagnetic wave of specified
end testing frequency modulation.
ROUTER  Deadline indicating a device that moves data between different network segments and is able to read the header of the data packet to determine the best route of transmission.The router can connect network segments using IP protocols
Spools of Ruhmkorff Operative act to generate tensions high value buttons, consists essentially of two electrical windings mounted on a cylindrical same core of ferromagnetic material.
Reostato     term coined by C. Wheatstone resistance variable resistor
Resonance: phenomenon on a physical system with a frequency characteristic (free oscillation)  
that happens all the time that a system is capable of swinging subjected to a series of periodic pulse frequency equal to or nearly one of the frequencies of oscillation of the system. When these conditions are satisfied the state of the system oscillates with an amplitude increases until  Reaches a maximum value in which energy is 
 absorbed by impulses from energy dissipated by the forces of friction.
Deadline indicating a computer and software that offer services to clients such as storing files (file server), programs (application server), sharing printers (print server), fax (fax server) or modem (Modem server) .
INTERNATIONAL SYSTEM OF MEASURE: a system of physical units in which the fundamental values have the length, time, mass, electric current, temperature, light intensity and  Quantity of the substance, and the corresponding units of measurement are the meters, the second, the kilogram, amp,kelvin, la candela e la mole. Kelvin, the candle and mole.
 Operative with two electrodes, generally spherical, adjustable distance, used for the evaluation of potential differences high.
The telegraphy (from the greek, writing distance learning) is a system  Communication for the transmission distance signal represent, in code, letters, numbers and signs of writing. The Telegraphy has ancient origins and can 'be divided into: acoustics, optical and electrical.
TESLA: units of measurement in the International System magnetic induction B (symbol T).
Transducer an apparatus that performs from one to another of the ways in which energy is manifested (Electrical, mechanical sound, heat, light).

VALUE QUADRATICO MIDDLE (RMS) is the square root of the square of the average size of a regular.For example, a sinusoidal signal, the mean square value is given by the magnitude of maximum magnitude of divided square root of two Aeff = AM /.  The root mean square value is used to simplify some formulas: for example, when you want to get the average power dissipated by an inductance, and / or capacity, and / or resistance in a circuit route from alternating current.
VOLT per METRO (V/m): means the unit of measure in the International System in the intensity of electric field (E). 1 V / m is the electric field between two places at a distance of one metre between which there is a Unlike potential of 1 volt.

World Wide Web Consortium (Consortium of 3 W). The W3C was created to lead the Web at the highest level, developing common protocols that enable its evolution and ensure interoperability between different systems. It is an international industrial consortium led by MIT Laboratory for Computer Science (MIT LCS) in the USA, the National Institute for Research in Computer Science and Control (INRIA) in France and Keio University in Japan. The services offered by the Consortium include: a complete record on the World Wide Web for developers and customers, implementation of codes of reference and different applications to demonstrate use of new technology.  Today, the W3C has more than 410 organizations. Term coined by Tim Berners-Lee (inventor of HTML) in 1990, shows all Internet servers that allow html pages and other services to be viewed through client applications called browser.

Wide Area Networks. Wide Area Networks. A WAN links between their networks.