H^* = H^′/t(X)

where X = {x₁, …, x_n} is the set of input characters x_i (i = 1, …, n) and $t\left(X\right)={\displaystyle \sum _{n=1}^{n}p(x_i)\cdot t(x_i)}$ is the mean value of the duration t(x_i) of a character x_i which occurs with probability p(x_i)

Note 1 to entry: The average information rate can be expressed in a unit such as the shannon per character and second.