# What is a Signal?

## Definition of Signal

A signal may be defined as a function of one or more independent variables like time, distance, position or temperature etc., that has some information about the phenomena that produced the signal.

COMPARISON OF PAM, PWM, PPM MODULATION TECHNIQUES

So in other words we can say, a signal is a function of independent variables having some information.
The signals maybe motion signals, sound signals, image signals or video signals etc.

# Continuous Time and Discrete Time Signals Video [HD]

Signals can be classified into two types based on their characteristics in time domain-
Continuous Time Signals (C.T.)
Discrete Time Signals (D.T.)

# Continuous Time Signals (C.T.)

A signal that is defined continuously with independent variable (time) is called a continuous time signal.

Some physical examples of continuous time signals are- sound signals, pressure signals, temperature signals etc. Other examples are- sine wave, triangular wave etc.
The image shown below is of a continuous time signal.

 Continuous Time Signal (C.T.)

This signal has some certain value at every instant of time, in any period of time interval. Therefore it is continuous in time, so called as continuous time signal.

# Discrete Time Signals (D.T.)

Discrete time signals are the signals that are defined only at discrete (distinct/separate) times.

Watch Large collection of Videos on Signals and systems here

It means discrete time signals are not continuous in time.
The following image shows a discrete time signal-

 Discrete Time Signal (D.T.)

From the image given above, it is clear that value of the signal is defined only at some integer values.
Integers are- (n= ...-2, -1, 0, 1, 2, 3, 4...).
You can see in this image that value of the signal at n=1 is 1, value at n= 2 is 2, value add n= 3 is 1 and so on. But there is no value of the signal between n=1 and n=2,
So it is clear that the signal is not defined for any other value of time that is present between integer values. So we can say that, this is not continuous in time. Therefore it is called as discrete time signal (D.T.)
Example of discrete time signal - Stock market index.

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AMPLITUDE MODULATION (TIME DOMAIN EQUATIONS AND WAVEFORMS)

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PULSE AMPLITUDE MODULATION (PAM)

COMPARISON OF PAM, PWM, PPM MODULATION TECHNIQUES

PULSE WIDTH MODULATION (PWM)

CONTINUOUS TIME AND DISCRETE TIME SIGNALS (C.T. AND D.T. SIGNALS)

NEED AND BENEFITS OF MODULATION

PULSE POSITION MODULATION (PPM)

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