Diagnostic diagrams for 3CR sources after the classification into HEG (blue circles) and LEG (red squares) made using the Excitation Index. Crossed circles are broad line galaxies, green crosses are extremely low [O III]/Hβ sources. Black triangles are sources for which the E.I. cannot be estimated, as they lack the measurement of one or two diagnostic lines. The filled symbols are derived from the new data presented in this paper.