... Seminar archive . ... The structure of the X-ray sources in the hard spectral state of accreting black-hole binaries has been a subject of intense debate. The paradigm dominant for many years postulated that the accretion disc in the hard state is truncated at some radius >> the innermost stable orbit (ISCO) whereas the disc reaches the ISCO in the soft state. ... On the other hand, there have been numerous claims in recent years that the disc extends to the ISCO in the hard state. ...