A signal is an electrical current that is used for carrying information from one system or network to another.
Analog signal is a continuous signal in which one time varying quality represents another time based variable.
Advantage of Analog Signal
- Easier in processing.
- It has a low cost and is portable.
- Uses less bandwidth.
This kind of signal works with physical values and natural phenomena such as earthquake, frequency, volcano, speed of wind etc.
It is a signal that is used to represent data as a sequence of separate value at any point in time.
Advantage of Digital Signal
- It can convey information with less noise.
- low cost configuration.
- More flexible
This type of signal represents a real number within a constant range of value.
Difference between Analog & Digital Signal.
- Infinite range of value.
- More exact value but difficult to work with.
- Finite range of value.
- Not as exact as analog but easier to work with.
What is data encoding ?
Data encoding is the process of converting a sequence of symbols, characters, alphabets or the data into a specified format for the secured transmission of data.
Decoding is the reverse process of encoding which is to extract the information from the converted format.
Encoding is the process of using various patterns of voltage or current level to represent 1s and 0s of the digital signals on the transmission link.
The common types of line encoding are unipolar, polar, bipolar and manchester.
Unipolar NRZ ( non return to zero)
Nrz code has 1 for high voltage level and 0 for low voltage level.
Polar NRZ – Level
Uses two different voltage levels (one positive and one negative) as the signal elements for the two binary digits.
- 1 = Negative voltage
- 0 = Positive voltage
Polar NRZ – Inverted
If a 1 occurs at the incoming signal, then there a occurs a transition at the beginning of the bit interval.
For a 0 at the incoming signal, there is no transition at the beginning of the bit interval.
- 1 = Transition (Change)
- 0 = No transition (No change)
Polar RZ ( Return to Zero)
- 1 = high to 0 (z)
- 0 negative to 0 (opposite z)
In this type of coding, the transition is done at the middle of the bit interval. The transition, for the resultant pulse is from high to low in the middle of the bit interval. For the input bit 1, while the transition is from low to high for the input bit 0.
- 1 = High to low voltage.
- 0 = Low to high voltage.
In this type of coding, there always occurs a transition in the middle of the bit interval. If there occurs a transition at the beginning of the bit interval, then the input bit is 0. If no transition occurs at the beginning of the bit interval then the input bit is 1.
- 1 = No transition
- 0 = Change