A simple encoder circuit is a [[one-hot]] to binary converter. That is, if there are of 2<sup>''n''</sup> input lines, and at most only one of them at most will ever be 1high, the binary code of this 'hot' line is produced on the ''n''-bit output lines.
For example, a 4-to-2 simple encoder takes 4 input bits and produces 2 output bits. The illustrated gate level example implements the simple encoder defined by the truth table, but it MUST be understood that for all the non-explicitly defined input combinations (i.e. inputs containing 0, 2, 3, or 4 high bits) the outputs are treated as don't cares.
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{{caption|4 to 2 Simple Encoder}}
If input circuit guarantees one and only one bit high on the input orcircuit ifcan itguarantee isat understoodmost thata non-single-active-inputswill produce garbage encodingsinput, a simple encoder is a better choice than a prioriy encoder, since it requires less logic to implement.
