ACT.#M1

                          MODEM DIAL UP CONNECTION

Dial-up Internet access is a form of Internet access that uses the facilities of thepublic switched telephone network (PSTN) to establish a connection to an Internet service provider (ISP) by dialing a telephone number on a conventional telephone line. The user's computer or router uses an attached modem to encode and decode information into and from audio frequency signals, respectively. Despite the proliferation of high-speed Internet access (broadband), dial-up Internet access may be used where other forms are not available or the cost is too high, such as in some rural or remote areas.

Dial-up Internet has been around since the 1980s via public providers such asNSFNET-linked universities and was first offered commercially in July 1992 bySprint.^[1

*MODERM*
                      


                    *    MODULATOR    *

                                 

An RF modulator (or radio frequency modulator) is an electronic device whose input is a baseband signal which is used to modulate a radio frequency source.^[1]

RF modulators are used to convert signals from devices such as media players,VCRs and game consoles to a format that can be handled by a device designed to receive a modulated RF input, such as a radio or television receiver.

              
                 

                    *    DEMODULATOR   *


A demodulator is an electronic circuit (or computer program in a software-defined radio) that is used to recover the information content from the modulated carrier wave




*BROAD BAND


                          *     CABLE    *

This article is about electrical cables. For other uses, see Cable (disambiguation).

Electrical cable cross section

6 inch (15 cm) outside diameter, oil-cooled cables, traversing the Grand Coulee Dam throughout. An example of a heavy cable for power transmission.

An electrical cable is made of two or more wires running side by side and bonded, twisted, or braided together to form a single assembly, the ends of which can be connected to two devices, enabling the transfer of electrical signals from one device to the other. Cables are used for a wide range of purposes, and each must be tailored for that purpose. Cables are used extensively in electronic devices for power and signal circuits. Long-distance communication takes place over undersea cables. Power cables are used for bulk transmission of alternating and direct current power, especially using high-voltage cable. Electrical cables are extensively used inbuilding wiring for lighting, power and control circuits permanently installed in buildings. Since all the circuit conductors required can be installed in a cable at one time, installation labor is saved compared to certain other wiring methods.

The term originally referred to a nautical line of specific length where multiple ropes, each laid clockwise, are then laid together anti-clockwise and shackled to produce a strong thick line, resistant to water absorption, that was used to anchor large ships. In mechanics, cables, otherwise known as wire ropes, are used for lifting, hauling, and towing or conveying force through tension. In electrical engineering cables are used to carry electric currents. An optical cable contains one or more optical fibersin a protective jacket that supports the fibers.

                         *      DSL      *

 DSL (Digital Subscriber Line) is a technology for bringing high- bandwidth information to homes and small businesses over ordinary copper telephone lines. xDSL refers to different variations of DSL, such as ADSL, HDSL, and RADSL.








                *SATILLITE *

In the context of spaceflight, a satellite is an artificial object which has been intentionally placed into orbit. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as Earth's Moon







                

                          *    WIRELESS   *

Wireless communication is the transfer of information between two or more points that are not connected by an electrical conductor.

The most common wireless technologies use radio. With radio waves distances can be short, such as a few meters for television or as far as thousands or even millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of applications of radio wireless technology includeGPS units, garage door openers, wireless computer mice, keyboards andheadsets, headphones, radio receivers, satellite television, broadcast televisionand cordless telephones.

Somewhat less common methods of achieving wireless communications include the use of other electromagnetic wireless technologies, such as light, magnetic, or electric fields or the use of sound.

It should be noted that the term wireless has been used twice in communications history, with slightly different meaning. It was initially used from about 1890 for the first primitive radio transmitting and receiving technology, as in wireless telegraphy, until the new word radio replaced it around 1920. The term was revived in the 1980s and 1990s mainly to distinguish digital devices that communicate without wires, such as the examples listed in the previous paragraph, from those that require wires. This is its main usage today.