Weeks 4: 
  DATA COMMUNICATION
   -to define data communication terminology
   -to detail the type of signal transmit through communication medium
   -describe data transmission mode
   -how network performance work


Communication
-Definition: collection and contribution of the electronic representation of information FROM and TO remote facilities by means of electrical transmission system such as telephone line,satelites or coaxial cable.
-there are two types of signals, analog signal and digital signal:

-frequency is a number of complete wave cycles. It is measured in Hertz(Hz) which is cycle per second.

-Amplitude is the wave height measures in Volt(V) or decible(dB). A strong signal will create higher   amplitude.

-Analogue signal is transmit through PSTN line known commonly as phone line.

-process changing ANALOGUE to DIGITAL =Modulation 

-process changing DIGITAL to ANALOGUE = Demodulation

-hardware used in computer to do this process is called MoDem

Data Transmission Mode

Parallel transmission

   -a group of bits is transmitted simultaneously by using a separate line for each bit.

Serial transmission

   -transmit all the bits one after another on a single line. This style is a bit slower compare to parallel

   -2 types of serial transmission mode:  # synchronous transmission 

                                                            # asynchronous transmission

Simplex

-data transmitted one direction only

-role of transmitted and receiver are fixed

-example: radio, video, tv

Half Duplex

-message can follow in 2 direction but NEVER at same time.

-one station transmit to another without interruption 

-other respon after transmission been complete.

-example: walkie- talkie.

Full Duplex

-both station can transmit and receive simultaneously 

-consists of 2 simplex channel

-phone call

Multiplexig

-a set of techniques that enable more than 1 device to combine and send their signals simultaneously through a single data links at the same time.

-network can transfer several different types of data : voice, video

-latest technology of LINKS=high - bandwidth media, coxial cable,optical fiber,satellite microwaves.

-each of these LINKS has a carrying CAPACITY.