class $\lambda$, this dip is [*always*]{} present as a transition between state and state , not only at the end of the long state C intervals, but also during the much more rapid flaring. By examining in detail the oscillations shown in Fig. 5, one can see that indeed a soft dip lies in between all -transitions, although the position in the CD in this case is much higher and in some cases it overlaps with that of state (this overlap will be discussed extensively below). Also, the dip in the light curve corresponding to state A is not as deep as in the previous case.

Moving to observation K-33-00 (class $\kappa$), an examination of a short sample of the light curve shows that, although the time scales are shorter, the source behaves like in the $\lambda$ case (see Fig. 7). This was already recognized by Belloni et al. (1997b), who based on these data their analysis of the disk instabilities for states B and C, but it also applies when state A is considered.

The main color loop
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It is useful to summarize the results from the first three classes before presenting more data. In the three observations 