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].
*MODEM
A modem (modulator-demodulator) is a network hardware device that modulatesone or more carrier wave signals to encode digital information for transmission and demodulates signals to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used with any means of transmitting analog signals, from light emitting diodes to radio. A common type of modem is one that turns the digital data of a computer into modulated electrical signal for transmission over telephone lines and demodulated by another modem at the receiver side to recover the digital data.
Modems are generally classified by the amount of data they can send in a givenunit of time, usually expressed in bits per second (symbol bit/s, sometimes abbreviated "bps"), or bytes per second(symbol B/s). Modems can also be classified by their symbol rate, measured in baud. The baud unit denotes symbols per second, or the number of times per second the modem sends a new signal. For example, the ITU V.21 standard usedaudio frequency shift keying with two possible frequencies, corresponding to two distinct symbols (or one bit per symbol), to carry 300 bits per second using 300 baud. By contrast, the original ITU V.22 standard, which could transmit and receive four distinct symbols (two bits per symbol), transmitted 1,200 bits by sending 600 symbols per second (600 baud) usingphase shift keying.
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
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.
A high-capacity transmission technique using a wide range of frequencies, which enables a large number of messages to be communicated simultaneously.
In telecommunications, broadband is a wide bandwidth data transmission with an ability to simultaneously transport multiple signals and traffic types. The medium can be coaxial cable, optical fiber, radio or twisted pair.
A thick rope of wire or nonmetallic fiber, typically used for construction, mooring ships, and towing vehicles.
An insulated wire or wires having a protective casing and used for transmitting electricity or telecommunication signals.
DSL is defined as an abbreviation that stands for digital subscriber line which is defined as the way a computer connects to the Internet at high speeds using telephone lines. An example of DSL is the phone service that might be down when your Internet connection isn't working.
An artificial body placed in orbit around the earth or moon or another planet in order to collect information or for communication.
Wireless is a term used to describe telecommunications in which electromagnetic waves (rather than some form of wire) carry the signal over part or all of the communication path. Some monitoring devices, such as intrusion alarms, employ acoustic waves at frequencies above the range of human hearing; these are also sometimes classified as wireless.
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