Encoder in Digital Electronics

An encoder is a digital circuit that performs the inverse operation of a decoder. An encoder has 2ⁿ (or less) input lines and n output lines. The output lines generate the binary code corresponding to the input value. An example of an encoder is the octal-to-binary encoder, whose truth table is given in the below table.

It has eight inputs, one for each of the octal digits, and three outputs that generate the corresponding binary number. It is assumed that only one input has a value of 1 at any given time; otherwise, the circuit has no meaning.