DATA COMMUNICATION...

•  Definition:

The collection & distribution of electronic representation of information from & to remote facilities

•  Format:

Raw data/information must digitized

Analogueà digital à analogue

• Types of signal:

* ANALOGUE

 - ex: human voice

- frequency & amplitude

- frequency measure by Hertz (Hz)

- amplitude measure by V & Db

* DIGITAL 

- 0 & 1 represent square wave

- transmit through PSTN line

- process analogue à digital = Modulation

- process digital àanalogue = Demodulation

-  hardware that used to do this process = Modem

• DATA TRANSMISSION MODE

#  Parallel - transmited simultaneously using separate line for each bit

# Serial - transmited all bits one after another on a single line & this slower compared to parallel

# Synchronous - use template (ex: in blog)

# Asynchronous - ex: emel

• DATA FLOW

# Simplex - in 1 direction

                                   - transmitter & receiver fixed

          - ex: radio, tv

#  Half Duplex - in 2 direction but not at same time

- Ex: telefon, walkie talkie

# Full Duplex - can transmit & receive simultaneously

-  consist 2 simplex

# Multiplexing - set of technique that enable more than 1 device to combine & send their    signals simultaneously through single data line at the same time