CBSE NOTES CLASS 12 PHYSICS
CHAPTER 15 COMMUNICATION SYSTEMS
Different types of signals
Information converted in electrical form and suitable for transmission is called a signal.
Noise refers to the unwanted signals that tend to disturb the transmission and processing of message signals in a communication system.
Analog signals are continuous variations of voltage or current. They are single-valued functions of time. Sine wave is the fundamental analog signal. All other analog signals can be understood in terms of their sine wave components. Examples - sound and picture signals in TV.
Digital signals are those which can take only discrete stepwise values. Binary system used in digital electronics uses just two levels of a signal. ‘0’ corresponds to a low level and ‘1’ corresponds to a high level of voltage/current.
The codes used to represent numbers, letters and certain characters constitue coding system. BCD (binary coded decimal), ASCII (American Standard Code for Information Interchange), EBCDIC (Extended Binary Coded Decimal Interchange Code) etc. are examples of coding systems.