Transfer functions |Γ_λ(ν)|² (top panel) and normalised transfer functions |Γ_λ, norm(ν)|² (bottom panel) in three wavebands: λ = 1300 Å (blue line), λ = 3000 Å (green line), and λ = 5000 Å (red line). The solid lines correspond to the case of an accretion-powered corona (case A) with L_transf/L_disc = 0.5 and the dashed lines to an externally powered corona (case B) with L_transf/L_disc = −0.5. The fiducial parameters are: M_BH = 8 × 10⁸ M_⊙, ṁ_Edd = 0.1, h = 20, Γ = 2, θ = 30°, E_cut = 150 keV, f_col = 1.7, R_out = 5000R_g, and α^* = 0.