I have just updated my TS-590S Digital HOWTO.New material includes a 4-page "Nutshell" section explaining the basic principles of AFSK, VOX and PTT operation in the radio.
To download the HOWTO, go to the TS-590S Resources Page: http://homepage.ntlworld.com/wadei/ts-590s.htm Scroll down to the "HOWTOs" section, then click on the link:"HOWTO set up the Kenwood TS-590S for Digital Data and Digital Voice Operation"
-- 73 Ian, G3NRW The TS-590S Resources Page: http://homepage.ntlworld.com/wadei/ts-590s.htm