Hi Cedric,
I have not done any testing with using CCM to PTT directly from the software to the RRC. With the K3, you can do direct CW/RTTY keying via serial commands which really makes digital modes very easy to do. I just simply take the RRC Speaker audio and feed it in the Mac's Audio IN (Line in) and decode. RUMlog integrates CCM into its interface, so when you TX, RUMlog sends the commands to the K3 via Serial, this is both PTT and RTTY/CW generation.
73!
Lee
WW2DX