Representative power spectra of the horizontal and diagonal branches at various flux levels for the fast-rotating pulsar 4U 0115+63 (up), EXO 2030+375 (middle) and the slow pulsator 1A 0535+262 (down). Note the shift toward higher frequencies at high flux. In 1A 0535+262, L₀ is not seen at low luminosities because it lies outside of the frequency interval considered. Other features such as L_LF in 4U 0115+63 or a QPO at ~40 mHz in 1A 0535+262 are shown. The Lorentzian profiles of the pulse peaks and the QPO were removed for clarity.