# Building Blocks of All Signals

Learn about how most practical signals are constructed from a finite or infinite number of sinusoids.

## We'll cover the following

A complex sinusoid is represented by a **single impulse** in the frequency domain.

- A real sinusoid is formed by the combination of two such complex sinusoids in time—hence, two impulses in frequency.
- To form any other signal,
complex sinusoids in time must be combined together.**more than two**

Similar to a house with bricks, these sinusoids form the basic unit of signal construction regardless of their shape. One *tick* on the frequency axis implies one complex sinusoid. When many of them combine together, they form a continuous curve in the frequency domain called the **spectrum** of that signal.

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