<P> μ - law expansion is then given by the inverse equation: </P> <Dl> <Dd> F − 1 (y) = sgn ⁡ (y) (1 / μ) ((1 + μ) y − 1) − 1 ≤ y ≤ 1 (\ displaystyle F ^ (- 1) (y) = \ operatorname (sgn) (y) (1 / \ mu) ((1 + \ mu) ^ (y) - 1) ~ ~ ~ ~ - 1 \ leq y \ leq 1) </Dd> </Dl> <Dd> F − 1 (y) = sgn ⁡ (y) (1 / μ) ((1 + μ) y − 1) − 1 ≤ y ≤ 1 (\ displaystyle F ^ (- 1) (y) = \ operatorname (sgn) (y) (1 / \ mu) ((1 + \ mu) ^ (y) - 1) ~ ~ ~ ~ - 1 \ leq y \ leq 1) </Dd> <P> The discrete form is defined in ITU - T Recommendation G. 711 . </P>

The characteristics of compressor in μ-law companding are