  In 2005 February we observed Cygnus X-1 over a period of 10 days
quasi-continuously with the Rossi X-ray Timing Explorer and the Ryle telescope.
We present the results of the spectral and timing analysis on a timescale of 90
min and show that the behavior of Cyg X-1 is similar to that found during our
years long monitoring campaign. As a highlight we present evidence for a full
transition from the hard to the soft state that happened during less than three
hours. The observation provided a more complete picture of a state transition
than before, especially concerning the evolution of the time lags, due to
unique transition coverage and analysis with high time resolution.
