Phase-space diagram (line-of-sight velocity vs. clustercentric radius, normalized by the protocluster velocity dispersion and the radius R₂₀₀, respectively) for the spectroscopically identified 31 members of the overdensity 7C 1756+6520. Different symbols refer to different types of protocluster members, as specified in the legend. RG refers to the central radio galaxy of the protocluster. The names of the AGN are also reported. The dashed horizontal line is drawn at v/σ_v = 0, corresponding to the systemic velocity of the protocluster.