Encoder

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Circuit diagram of a single bit 4-to-2 line encoder

A₃	A₂	A₁	A₀	F₁	F₀
0	0	0	1	0	0
0	0	1	0	0	1
0	1	0	0	1	0
1	0	0	0	1	1

Truth table

An encoder is a device used to change a signal (such as a bitstream) or data into a code. The code may serve any of a number of purposes such as compressing information for transmission or storage, encrypting or adding redundancies to the input code, or translating from one code to another. This is usually done by means of a programmed algorithm, especially if any part is digital, while most analog encoding is done with analog circuitry.

[edit] Examples

A compressor encodes data (e.g., audio/video/images) into a smaller form.
A multiplexer combines multiple inputs into one output.
A rotary encoder converts rotary position to an analog (e.g., analog quadrature) or digital (e.g., digital quadrature, 32-bit parallel, or USB) electronic signal.
A linear encoder similarly converts linear position to an electronic signal.