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Data must be transformed into electromagnetic signals prior to transmission
across a network.
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Data and signals can be either analog or digital.
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A signal is periodic if it consists of a continuously repeating pattern.
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Each sine wave can be characterized by its amplitude, frequency, and phase.
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Frequency and period are inverses of each other.
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A time-domain graph plots amplitude as a function of time.
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A frequency-domain graph plots each sine wave’s peak amplitude against its
frequency.
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By using Fourier analysis, any composite signal can be represented as a
combination of simple sine waves.
