Hi,

Thanks everybody for the help and suggestions.

I have heard through other users of the Kenwood 90 series
radios that the factory cable has the MAX232 chip within
one of the connectors, as well as a data combiner circuit
that sends/receives information over 1 data line through the
radios microphone connector. The radio deals with 5 volt TTL
signals and not the 12 volt rs-232 voltages. If you open your
factory cable, you will probably see these circuits and can
verify what I have heard.

Mike