From that beginning, a system of train dispatching evolved. The operating rule book, later standardized for all railroads, contained the basic rules for the operation of trains, such as the meaning of the all fixed, audible and hand signals; the form, format and meaning of train orders; and the duties and obligations of each class of employee. The operating, or official, timetable established train numbers and schedules; meeting points for those trains; showed the length of passing tracks at each station as well as indicating the locations where train orders might be issued and contained a variety of other information which might be necessary or useful to train crews operating trains over the territory covered.