we have discussed so far, we could identify three basic states:

-   [**]{}: high rate, high HR$_1$;

-   [**]{}: low rate, low HR$_1$, variable HR$_2$ depending on the length of the event;

-   [**]{}: low rate, low HR$_1$ and HR$_2$

As far as the transitions between the three states go, in two cases (classes $\lambda$ and $\kappa$), the source invariably follows the sequence: ---and so on. In the third case (class $\theta$), there are only oscillations between two states (and ). No direct transition from state to state is observed. A schematical representation of this can be seen in Fig. 8. Notice that in some observations, state is not completely separated from state in the CD: this blending between the two classes is discussed extensively in the following sections. Before discussing this diagram however, we must go through the other classes.

Class $\chi$: state only
------------------------

As described before, class $\chi$ is characterized by the absence of strong variability and HR$_2>$0.1. A large number of observation intervals belonging to this class correspond to observations taking place during three periods when no strong variability was observed on long (hours to months) time scales with the RXTE/ASM. The three periods are identified 