It is one of my semester project presentation along with my group members, of subject Data Communication, which covers a brief intro about all the vital things related to the modems.

2. MODEMs

3. GROUP MEMBERS
 Numan Ahmad Naseer
 Muhammad Masaud Ahmad
 Ahmad Osman Salad
 Syed Shujat Ali

4. TABLE OF CONTENTS
 Introduction to Modem
 What is Modem?
 History
 Types of Modem
 Modem commands
 Functions of the Modem
 References

5. INTRODUCTION
 A modem (modulator-demodulator) is a device that
modulates an analog carrier signal to encode digital
information, and also demodulates such a carrier
signal 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 over any means of transmitting
analog signals, from light emitting diodes to radio.

7. WHAT IS MODEM.?
 Modem, short for modulator-demodulator is an
electronic device that converts a computer’s digital
signals into specific frequencies to travel over
telephone or cable television lines.
 At the destination, the receiving modem demodulates
the frequencies back into digital data.
 Computers use modems to communicate with one
another over a network.

9. History
 IN 1920 used as
multiplex equipment
 In 1958 used in air-
defense system
 In 1960 the name
Data-Phone was
introduced
 In 1962 The famous
Bell 103A dataset
standard was also
introduced by AT&T

10. TYPES OF MODEMS
External Vs. Internal Modems
 External Modem: This is a modem separated from
the system unit in the computer case. It is connected
to the serial port of the computer by means of a
cable. It is connected to the telephone wall jack by
another cable.
 Internal Modem: An internal modem is a circuit
board (a modem card) that can be added to the
system unit of the computer. It takes one of the
expansion slots.

11. Standard Vs. Intelligent Modems
 Standard Modems: Most modems used today
are called standard modems. These modems are
usually operated by commands entered from a
microcomputer keyboard.
 Intelligent Modems: Intelligent modems are also
called advanced modems. These modems can
accept new instructions and then respond to the
commands while transmitting data and
information.

12. Short- Haul vs. Wireless Modems
 Short-Haul Modems: Short- haul modems are
devices that transmit signals down the cable through
any COM1 port.
 Wireless Modems: Wireless modems transmit the
data signals through the air instead of by using a
cable. They sometimes are called a radiofrequency
modem.

13. Smart Modem
 It is a standard modem with micro-processor.
Features of smart modem are following:
 Auto dial
 Auto answer
 Auto fallback
 Accept commands

15. Modem Commands
 Modems can receive and act on commands from
computer terminal
 These commands begin with symbol AT
 The range of commands is called the AT Command
Set

16. The AT Command Set
Hayes Corporation developed smart modem
that accepted AT type commands. Following is the list of
AT commands:
 ATA Answer call
 ATA Repeat last command
 ATC Turn modems carrier signal ON or OFF
 ATD Dial telephone number
 ATE Enable(ATE1) or disable(ATE0)
 ATH Hang up phone(ATH0) or pick up phone(ATH1)

17. The AT Command Set
 ATM Turn on modem speaker(ATM1) or turn
off(ATM0)
 ATO Place modem on-line
 ATS Set values in modem “S” registers
 ATT Touch tone dial
 ATZ Reset the modem

18. ITU V.XX Modem Standards
The International Telegraphic Union(ITU) is an
international organization responsible for establishment
of world V standards.

19. ITU V.XX Modem Standards
V Series Standards Details
V.22 1200bps full duplex 2 wire dial-up for use in telephone
networks
V.22 bis 2400bps dial-up or wire leased line
V.23 600/1200bps dial-up for use in telephone network
V.26 bis 2400/1200bps dial-up for use in telephone network
V.32 9600bps dial-up for use in telephone network
V.34 28800bps dial-up for use in telephone network or
leased line,synchronous .
V.35 48Kbps using 60-108Khz group-band circuits

20. FUNCTION OF MODEMS
 Error Correction
 Compressing the Data
 Flow Control

21. ADVANTAGES

22. WHAT’S HAPPENING TODAY?
 Faster non-analog modems
 Users connect to the internet through a:
1. Cable modem
2. Local area network(LAN) connection
3. Digital subscriber line (DSL) connection

23. Cable Modem
 Cable company offers internet access over the cable
 Speed at more than 1 mbps or about 20 times faster
that 56 k modems
 Downstream data into a 6-MHZ channel look just like
a TV channel
 Equipment:
1. Cable Modem
2. CMTS (cable modem termination system)

25. Digital Subscriber Line (DSL)
 Digital subscriber line
 Very high speed connection
 Uses the same wires as a regular telephone line
 DSL transceiver
 DSL access multiplexer (DSLAM) at DSL service
provider

27. REFERENCES
 http://en.wikipedia.org/wiki/Modem
 http://www.tahirmehmood.com/wp
content/uploads/2011/01/dslsetup.png
 http://www.wisegeek.com/what-is-a-modem.htm
 http://e99ie.tripod.com/ADSL_Tutorial/purpose.htm
 http://amylouisewebber.files.wordpress.com/2012/02/tha
nkyou2.jpg
 http://home.olemiss.edu/~misbook/cs11.htm
 http://www.scribd.com/doc/27121008/Functions-and-
Types-of-Modems
 http://www.ustudy.in/node/5016