Signals and Systems

Single Channel Signals

Signals which are generated by a single source or a single sensor are called as single channel signals. Speech signal is an example of single channel signal as it is generated from single source or a single sensor.

Multichannel Signals

If the signal is a function of one or more dependent variable generated by multiple sources or multiple sensors, represented in vector form then the signals are called as multichannel signals. For example color TV pixel can be described by 3 intensity functions I­_R, I_G, and I_b. Intensity in multichannel signal can be represented as,

Also intensity of image at any point can be function of x-axis, y-axis and time't'. Hence, a color TV pixel is a 3 channels and 3-dimensional signal.

	Continuous Time Signal		Discrete Time Signal
1.	A signal x (t) is said to be continuous type if it can be defined for continuous values of the independent variable.	1.	A signal x [n] is said to be discrete type if it is defined only at discrete time for set of discrete values (integer) of the independent variable.
2.	The symbol 't' is used to denote continuous time independent variable.	2.	The symbol 'n' is used to denote the discrete time independent variable.
3.	The independent variables are enclosed in parenthesis ( ).	3.	The independent variables are enclosed in brackets [ ].
4.	The continuous time signal x (t) can be defined by fractional values as well.	4.	The discrete time signal x [n] is defined only for integer values of independent variable.
5.	Continuous-time signals are the source signals of analog type.	5.	Discrete time signals can be obtained from sampling of continuous time signal.
6.	A speech signal as a function of time and atmospheric pressure as a function of altitude are examples of continuous time signals.	6.	Signals such as demographic data (as average budget, crime rate, pounds of fish caught etc.) are examples of discrete time signals.