  The HI Balmer emission lines of black-hole binaries show double-peaked
profiles during the high-soft state and the quiescent state. In the high-soft
state the profiles are asymmetric with a stronger red peak, but the profiles
are symmetric in the quiescent state. We suggest that in the high-soft state
the emission lines originate from the temperature-inversion layer caused by
irradiative heating of an optically thick accretion disk. Irradiative heating
also causes the formation of a disk wind, which mildly absorbs the blue peak of
the lines. The double-peaked lines seen in the quiescent state arise from an
optically thin disk. In the absence of a disk wind, the lines are unabsorbed
and so the symmetry of the line profiles is preserved.
