Assalamualaikum
1.Introduction
Data communication is process of change / transfer information in a form of a digital data (binary) in between two or more devices using electronic delivery system.
Data communication is transmitted via medium such as wires, coaxial cables, fiber optics, radiated electromagnetic waves such as broadcast radio, infrared light, microwaves and satellites.
2.Type of signal
Data cames in variety styles text, voice, picture and video.
Analogue Signal
Like a human voice. Formed by continuously varying voltage level that create wave than be grasped by an analogue transmitter like microphone.
Frequency is a number of completed wave's cycles. Measured in Hertz (Hz), which is cycle per second.
Amplitude is wave's height that measured in voltan (V). A strong signal will create higher amplitude.
Digital Signal
Transmission of binary electrical or light pulses that only have two possible states, 0 and 1 ( language of computers). Presented as a square wave.
The process of changing :
1. Analogue to digital signal : modulation
2. Digital to analogue signal : demodulation
Modem is the hardware used to do changing process.
3. Data Transmission Mode
Parallel Transmission
Data is sent at least one byte at the time, each bit in the byte taking separate path. Means that a group of bits is transmitted simultaneously by using separate line for each bit.
Serial Transmission
Data sent one bit at time, one after another a long a single path. A bit slower compared to parallel transmission. For example between computer to printer.
3 Serial transmission mode
1.Synchronous transmission (serentak)
2.Asynchronous transmission (data lain yang dihantar bersama) Example:keyboard
3.Isochronous transmission. Example: streaming voice, video and music.
4. Direction of data transmission
1.Simplex- one way communication. Never allows transmitting back. Example radio station
2.Half duplex- 2 direction but never at the same time. Example walkie-talkie
3.Full duplex- moves both direction at same time. Example telephone
5.Data compression
Encoding information using fewer bits than original representation. Example of file compression formats such as ARC and ZIP.
Before the class dismiss, we've been asked to create a mind map using the application "mindomo" and send it to the elearning by using format png.
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