Analog communication and digital communication
Based on the type of signals transmitted, communication electronics can be classified as,
1. Analog communication and
2. Digital communication
1. Analog communication
In analog communication, analog signals are used. An analog signal is a continuously varying voltage or current. Traditionally, in telephone and radio systems, the messages consisted of information conveyed by voice. The voice signal is an analog signal and so could take on any value within the overall range allowed. For example, if the telephone system were set up to handle voice signals, which ranged from 0 to 1 volt, the values transmitted at any instant could be 0.345 V, 0.179 V, and so on. This is called analog signal communication, because the signal can be any value within the range.
Shortcomings of analog communication
The greatest technical problem with an analog communication system is noise. Noise that comes from any part of the system - the modulator, the transmitter, the communication link, the receiver or the demodulator - can corrupt the signal.
Analog system do not offer opportunities for identifying corrupted signals.
A digital communication system offers many advantages to the user, that cannot be achieved with an analog system. Digital communications system may make use of analog links and concepts.
A digital system is a more general case of a binary system. In binary system, only two signal values can exist. They are often called 0 and 1, but these names represent specific voltages.
The term data is commonly used in digital communication systems. Data is any form of information, that has been put into digital form, so that it can be handled by a digital system. The data itself is measured as bit. (bit is a contraction of the term 'binary digit')
The binary signals are easy to generate and process with digital circuits. These digital circuits are available in the IC form and can generate and process digital data at high speeds.
1. The transmission quality is high and almost independent of the distance between the terminals.
2. The capacity of the transmission system can be increased.
3. The newer types of transmission media such as light beams in optical fibers and wave guides operating in the microwave frequency extensively use digital communication.
1. A digital system requires larger bandwidth.
2. It is very difficult to gradually change over from analog to digital transmission.