There are two variable parameters in general:

1. Amplitude
2. Time

The following operation can be performed with amplitude:

Amplitude Scaling

C x(t) is a amplitude scaled version of x(t) whose amplitude is scaled by a factor C.

Addition

Addition of two signals is nothing but addition of their corresponding amplitudes. This can be best explained by using the following example:

As seen from the diagram above,

-10

-3

3

Subtraction

subtraction of two signals is nothing but subtraction of their corresponding amplitudes. This can be best explained by the following example:

As seen from the diagram above,

-10

-3

3

Multiplication

Multiplication of two signals is nothing but multiplication of their corresponding amplitudes. This can be best explained by the following example:

As seen from the diagram above,

-10

-3

3

The following operations can be performed with time:

Time Shifting

x(t $pm$ t₀) is time shifted version of the signal x(t).

x (t + t₀) $to$ negative shift

x (t – t₀) $to$ positive shift

Time Scaling

x(At) is time scaled version of the signal x(t). where A is always positive.

|A| > 1 $to$ Compression of the signal

|A|

Note: u(at) = u(t) time scaling is not applicable for unit step function.

Time Reversal

x(-t) is the time reversal of the signal x(t).