Flux obtained from the combined time-averaged spectrum gathered for EC 01541−1409 across the two FORS chips (top panel) together with the wavelength-dependent amplitude (middle panel) and phase (bottom panel) extracted for the dominant 140.5 s mode. The flux and the amplitude spectra have been normalised to unity and are consequently dimensionless quantities, while the phase is plotted relative to its average value in the blue part of the spectrum in radians. The spectral lines identified are marked by vertical lines propagating across all plots: black continuous lines indicate hydrogen Balmer lines, dashed blue lines denote He I lines, and dotted red lines show He II lines.