T^* = T^′/t(X,Y)

where X = {x₁, …, x_n} is the set of input characters x_i (i = 1, …, n), Y = {y₁, …, y_m} is the set of output characters y_j (j = 1, …, m) and $t\left(X,Y\right)={\displaystyle \sum _{i=1}^n{\displaystyle \sum _{j=1}^{m}p(x_i,y_j)\cdot t(x_i,y_j)}}$ is the mean value of the duration t(x_i,y_j) of the pair of characters (x_i,y_j) which occurs with joint probability p(x_i,y_j).

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