BY

THE BIRTH OF INTERNET

Seeds of internet were planted way back in 1979 ,when U.S military forces used it to communicate in better, organized and safer way at ARPA (Advanced research project agency).

President of U.S was the first citizen to share this sophiciticated network to manage and share all important information.

Gates of internet were open to general public by early 90’s.

INTRODUCTIONWith the introduction of

internet, world changed

quickly.We can experience world

coming closer day by day

by use of internet. ISP (internet service

provider ) provides us with this internet facility. MODEM is a most important hardware that

connects us and ISP and helps us to access this valuable gift ‘INTERNET’.

WHAT IS MODEM ???

A Modem (made of Modulator &

Demodulator) is a device that

converts data from digital

computer signals to analogue signals that are

generally ,sent over a phone line.    

CONNECTING WORLDThe sending modem modulates the data into a

signal that is compatible with the phone line, and the receiving modem demodulates the signal back into digital data. Wireless modems convert digital data into radio signals and back.

                                       

                                                                                

•Modem is a full duplex device having modulator and demodulator.

•Modulator converts digital to analogue signals and sends info via LAN whereas demodulator receives info and converts analogue signals to digital signals.

WORKING OF MODEM

INTERNAL VIEW OF MODEM

TYPES OF MODEMS

MODEM

CABLE MODEM WIRELESS MODEM

1. Cable Modem

A cable modem is basically used for the one-one basis or to connect multiple computers inside a building as the signals degrade as more users come online.

Cable modem uses broadband Internet connection that is designed to operate over cable TV lines

FREQUENCY

STREAM

Downstream data -- data sent from the Internet to an individual computer -- into a 6-MHz channel.

Upstream data -- information sent from an individual back to the Internet

WIRELESS MODEMSWireless modem is a modem which connects to a wireless network instead of to the telephone system.Wireless modems operate at speeds comparable to dialup modems, not anywhere near the speed of broadband Internet connections.Some wireless modems attach directly to your notebook computer or PDA.

DIFFERENT TYPES OF WIRELESS MODEMS

Types of connections

DSL connection

Dialup connection

Broadband connection

DIAL-UP

Data is transmitted through an analog phone connection. An analog connection is the slowest type of connection available, and will not permit you to use your telephone for a voice connection at the same time that you are connected to the Internet. Dial-up connections allow only one computer at a time, per line, to be connected.

FEATURES

Slow and EconomicalConnection to network is established by dialing a

number provided by ISPQuality not so good because of telephone linesPhone modems only travel at speeds of 28.8k and 56k

and less.

DSL DSL means Digital Subscribers LineThis is a method of transmitting data over telephone

lines prevalent in many countries. DSL connection uses existing 2-wire copper

telephone line connected to the premise and will not tie up your phone as a dial-up connection does.

DSL uses a sophisticated modulation scheme to pack data onto copper wires.

TYPES OF DSL

All types of DSL technologies are collectively referred to as xDSL.

xDSL connection speeds range from 128 Kbps to 8 Mbps.

Two other types of DSL technologies are High-data-rate DSL (HDSL),Very high DSL (VDSL),Asymmetric Digital Subscriber Line(ADSL) and Symmetric Digital Subscriber Line (SDSL)

Advantages of DSL

The speed is much higher than a regular modem (1.5 Mps vs. 56 kps)

DSL doesn't necessarily require new wiring; it can use the phone line you already have.

Modem generally comes with company.

Disadvantages of DSL :

Service is better ,when you are near service provider. Sending data slower compared to receiving. The service is not available everywhere.

BROADBAND

Cable Internet works by using TV channel space for data transmission, with certain channels used for downstream transmission, and other channels for upstream transmission.

Coaxial cables are used by Broadband connection provides much greater bandwidth than telephone lines

Broadband connection can be used to achieve extremely fast access.

Its speed ranges from 512 Kbps to 20 Mbps.

Broadband connection

FEATURESBroadband connection use complex waveforms to

carry digital data. They are more advanced devices than traditional

dial-up modems as they are capable of modulating/demodulating hundreds of channels simultaneously.

New types of broadband modems are beginning to appear, such as doubleway satellite and powerline modems.

Transfer rates are affected by the number of subscribers online simultaneously.

Broadband connections can be used by individual subscribers to connect one computer to one line, or can be used to connect multiple computers in a building to the Internet.

DSL vs CABLE

Cable modem speeds are upto two times faster compared to DSL modem.

Speeds in cable modem fluctuates depending on the number of subscribers on the network.but this is not the case in DSL.

DSL boasts a bit better security compared to cable modem.

Thank you

Prepared by:-jigar.p.patelRoll no:-20Class:-sybba(itm)sem-4Collage:-cppatel&fhshah

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