This document discusses computer modems and their use in network communication. It explains that a modem converts digital data to analog signals for transmission over phone lines and vice versa. It describes different types of modems, their requirements, and how they connect computers via telephone lines to provide internet access and transfer of data and information over distance.

2. COMPUTER
NETWORKS

3. COMMUNICATION
OVER MODEM

4. After the completion of this lesson you will be
able to explain:
 Explain the characteristics of Modem.
 Identify and describe the requirement of
modem.
 Describe the types of modem.

5.  The word "modem" stands for "modulator-
demodulator". A modem's purpose is to
convert digital information to analog
signals (modulation), and to convert analog
signals back into useful digital information
(demodulation).

7.  Modems can be classified in various ways. Some
of the common types include – half-duplex
modem, full-duplex modem, 2-wire modem, 4-
wire modem, synchronous and asynchronous
modems.
 This device assists computer in transferring data
and information over telephone lines.

8.  Require dial up connection
 On sending end modem accepts digital data and
convert it into analog signals for transmission
over telepone lines.(modulation)
 On receiving end modem convert analog signal
back to digital signals.(demodulation)

12.  Used to connect micro computers.
 Provide high speed internet access.
 Connect computer via USB or ethernet port.
 Wireless DSL modems are also available for
connecting wireless devices.
 DSL modem convert digital signals into analog at
high frequency signals that are carried by telephone
lines and vice versa.

16.  ISDN "Modems" To use ISDN you must have a
special ISDN telephone line supplied by your
telephone company at additional cost. An
ISDN "modem" is really a Terminal Adapter
(TA). Like analog modems, there are internal
ones on cards and external ones that connect to
serial ports.