Thanks Nate,
Great reference. I haven't read it thoroughly yet, but a quick skim doesn't show anything related to different handsets, assigning ringtones to either internal or external, etc. This reference seems to be about configuring 3CX to identify to the handset whether it's internal or external, but is there more that then needs doing to tell the handset what ringtone to use for each? Do some handsets support this feature but not others?
Ben