Method for transmitting an information representative of the number of spreading codes allocated to the mobile stations in communication with a base station of a mobile telecommunication system, wherein it includes the step of: forming a word, said transmitted word, the content of which is representative of the number of spreading codes allocated, including in each transmission burst a general midamble resulting from the sum of selected midambles among all the available midambles, said selection being done by said base station in relation with said transmitted word so that a selected midamble corresponds to a binary element of said transmitted word equal to a first value and a non-selected midamble corresponds to a binary element of said transmitted word equal to second value, considering a received word the elements of which are in one-to-one relationship with the temporal positions of the estimations respectively corresponding to said available midambles.