INTERNET:(phisical aspect)

WEB:

www= world wide web, the web is a virtual web and information retrieval service.

To retrieval=to recover.

Is the leading information retrieval service of the internet. The web gives users access to a vast array of documents that are connected to each other means by means of hypertext or hypermedia links. The web operate with CLIENT and SERVER.

SERVER: are a computer programs that stores and send information to client upon request, and store and transmit documents to other computers on the network.

CLIENT: are programs that request documents.

BROWSER SOFTWARE: allow users to view the retrieved documents. Software that reads and displays hypertext and hypermedia documents on the internet. The first browser is Mosaic.

E-MAIL: is a most popular service offer of internet, you can sent message to another person or many people via computer.

SIGNALS:

The word digit (means cifra) come latin word digitus which means finger. In past finger where used to counts.

The digit is use 0 o 1, zero stands (off) and the current is not flowing in the circuit, 1 stands (on) current is flowing. Switches can be in one of 2 possible states, on or off.

Nowadays communication can be: oral, written, digital, gestures.

Information is processed and stored in the form of electric signals, and electric signals are processed by integrated circuits which that can only be in one of two possible states.

MORSE: Whit his code of dots and dashes for letters and numbers he can be consider a force runner of digit signals.

Digit communication is increasingly popular. It involves transmission of information via computers.

AMPLIFIER APPLICATIONS:

Increase of intensity of current. Amplifiers in electronics are devices that respond to a small input signals. Amplifiers of various types are widely used in such electronic equipment and computers.

A single amplifier is usually insufficient to raise the output to the level. In such cases output of the first amplifier is fed to a third, and so on cascade or multistage.

-An electronic amplifier is designed to produce a magnified identical to the output signal.

Amplifier does not amplify equally at all frequencies, the result is called frequency distorsion, or discrimination.

DISTORSION: as in emphasising bass or treble sounds in music recordings.

TELECOMUNICATIONS: are the transmission of messages that is (sounds, words, pictures) in the form electric signals other long distances in a fraction of a second.

Currently telecommunication means transferring information from pc to pc, to telecommunicate you need a computer, a modem connected to the computer and the telephone line and a telecommunication software.

Most telecommunications system transmit messages either through wires and cables or by means of radio waves and satellite links.

There are two methods of telecommunications transmission, analogue and digital.

ANALOGUE: transmission uses signals that are exact reproductions of the sound or picture being

transmitted. For example, an analogue telephone system transmits an electric current

that copies the pattern of sounds waves of the speaker's voice.

Digital transmission is more efficient than analogue and produces less noise and distortion.

Most telecommunication system are being converted from analogue to digital transmission.

MODEM: we need a modem because with it's device we have a bridge between digital signals(computer) and analogue signals(telephone).

The word modem is an acronym for Modulator/Demodulator.

When a modem modulates, it send rapid on/off pulses. The computer, on the other end, translates(demodulates) those signals into intelligible text or graphics.

Modem transmission speeds are measured in Kilobits per second.