1. Modem A Presentation Department of Computer Engineering,
M.S.P.V.L.Polytechnic College,
Pavoorchatram.

2. Modem Introduction: A modem [Modulator -Demodulator] is a device.
Data communication means transmitting digital information form one computer to other computers through the comuunication channels.

3. Modem

4. Cont.,
Communication between computers through the existing telephone cables.

5. Structure of data communication through modem
Analog data
Digital data

6. Working principle
The digital data from the computer is converted into analog data by the modem and are transmitted over the telephone line.

7. Cont.,
The analog data received from the telephone line is converted to digital by the modem and is given to the computer.

8. RS232 interface
This interface is used to connect computer and modem through serial port using standard RS232C.
The user communicated to the modem with the help of Hays commands through this interface.

9. Memory Processor and Memory
This unit is used to control the operations of the modem with respect to the Hayes commands.
DTP - Dynamic Trunking Protocol `switches are used to set auto answering.

10. Modem Modem data pump and signal processor
This unit receives serial data and gives it to the modulator.
It receives demodulated data from the demodulator and gives it to the modem processor.

11. Modulator
This unit is used to convert the digital data from computer into analog data. This process is called modulation.
This is done by adding a carrier signal to the digital signal.

12. Cont., 1
Amplitude
modulation 1 1 1

13. Demodulator
This unit is used to convert the analog data from telephone system into digital data.
This is done by eliminating the carrier signal from analog signal. 1 1 1 1
Demodulation

14. Phone interface Connect modem with the phone socket.
Dial the umber for making communication.
Detect the incoming ring signals.
Connect speaker for giving voice information , ring tone , data tone, engaged tone etc.,

15. Phone Socket

16. Types of modems
Two types of modem.
External modem
Internal modem

17. External modem
External modem is separate device and is kept outside the computer.

18. Internal modem
Internal modem is a part of the computer and is connected inside the system.

19. Installing Switch off the computer and connect the modem.
The computer is switched on , it detect the modem and displays new hardware found dialog box.
Insert the installation CD.

20. Cont.,
After completing installation close the windows and restart the computer.
Test the modem by the phone dialer option given in the accessories.

21. The END
….Thank you…