Analog Signals and Digital Signals - Analog Signals, Digital Signals, Analog To Digital And Back Again
information convey
A signal is any time-varying physical quantity—voltage, light beam, sound wave, or other—that is used to convey information. Analog signals convey information by analogy (i.e., by mimicking the behavior of some other quantity). Digital signals convey information by assuming a series of distinct states symbolizing numbers (digits). Both analog and digital signals are essential to modern communications and computing, but the greater simplicity and generality of digital signaling has encouraged an increasing reliance on digital devices in recent decades.
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An analog signal varies in step some other physical phenomenon, acting as an analog to or model of it. For example, the electrical signal produced by a microphone is an analog of the sound waves impinging on the mike. The term analog is also commonly used to denote any smoothly varying waveform, even one (e.g., the voltage available from an AC power outlet) that does not convey information. Any wa…
Digital signals convey discrete symbols that are usually interpreted as digits. For example, a voltage that signals the numbers 1 through N by shifting between N distinct levels is a digital signal, and so is a sinusoid that signals N digits by shifting between N distinct frequencies or amplitudes. (The latter would be analog as regards its waveform, but digital as regards its signaling strategy.)…
Because most physical quantities can be described by measurements, and because any measurement can be represented by a sufficiently long series of 0s and 1s, it is possible to transfer some of the information in any analog signal to a digital signal. In fact, according to the Nyquist sampling theorem, sufficiently precise measurements of an analog waveform made at twice or more the maximum frequen…
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