10-08-2012, 03:40 PM
Data and Signals
Data and Signal.ppt (Size: 1.26 MB / Downloads: 87)
One of the major functions of the physical layer is to move data in the form of electromagnetic signals across a transmission medium.
The data usable to a person or application are not in a form that can be transmitted over a network.
ANALOG AND DIGITAL
Both data and the signals that represent them can be either analog or digital in form.
Analog data refers to information that is continuous such as :
Analog clock that has hour, minute, and second hands gives information in a continuous form.
The sounds made by human voice, take on continuous values.
Digital data refers to information that has discrete states. Such as :
Digital clock 8:05.
Data are stored in the computer memory in the form of 0s and 1s.
PERIODIC ANALOG SIGNALS
Periodic analog signals can be classified as simple or composite.
Simple periodic analog signal such as Sine wave.
Composite periodic analog signal is composed of multiple sine waves.
The sine wave is the most fundamental form of a periodic analog signal. Each cycle consists of a single arc above the time axis followed by a single arc below it.