For an illustrative description of the possible redshift-dependence of the overall modified background model, we show the SZE-21 cm (in units of brightness temperature relative to the CMB) for a thermal plasma at temperature kT = 7 keV and with τ = 5 × 10^-3 for the modified CMB spectrum with the values of z taken from the original model (solid line), and for a modified CMB spectrum in which all components are globally shifted in frequency by a factor 3 (dashed line).