This presentation includes the function of the modem, types of modem

1. Modem
Introduction:
• A modem [Modulator -Demodulator] is a device.
• Data communication means transmitting digital
information form one computer to other computers
through the comunication channels.
• Communicate equipment used for long distance data
transfer through telephone lines.
• A pair of modems are needed to communication

2. Modem

3. Cont.,
• Communication between computers
through the existing telephone cables.

4. Structure of data communication
through modem
Analogdata
Digital data

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

6. Cont.,
• The analog data received from the telephone line is
converted to digital by the modem and is given to
thecomputer.

7. • 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.
• This interface is used to connect computer and
modem through serial port using standard
RS232C used in external modem for bits
conversion.

8. 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.

9. Cont.,
0 01 1 0 1
1 0 1 0 1Amplitude
modulation

10. 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 0 1 0 1 1 0 1 0 1 0
Demodulation

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

12. Phone Socket

13. Types of modems
Two types of modem.
 External modem
 Internal modem

14. External modem

15. External modem
• External modem is separate device and
is kept outside the computer.
• A 9 pin (DB9) or 25 pin serial cable connects
the PC serial port to the modem. Thus CPU
need not be opened during modem installation.
• External modems avoid hardware conflicts such
as (conflict of I/O address lines and that of
interrupt lines) the external modem setup is
faster and easier than internal modems.

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

17. Internal modem
• Internal modem that plugs directly into PCI or ISA
expansion slot.
• Peripheral Component Interconnect
• Industry Standard Architecture
• modulator converts digital data from computer into
analog signal which is transmitted through RJ-11
jack. (Registered Jack)
• On receiver side receive the analog signal
and pass them to demodulator it converts
signal and sends to UART. (Universal Asynchronous
Receiver/Transmitter)

18. Internal modem
• It then converts serial bit data into parallel
byte
• Controller is used to manage overall
operation of modem
• Non-volatile RAM (NVRAM) it stores modem
parameters.

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