[Elecraft] Pinout RS232 Plug for XV144?

[Martin]

Elecrafters,
i purchased a used internal K3 2m Transverter. I would like to check and
update the firmware.
For this, i need the pinout for the 3 pin stereo plug. I have real rs232 
interfaces on my computer and will make a cable on my own. I suspect i 
will need pins 2 , 3 and 5 from the D-sub 9 connector, but don't know 
where they will go on the 3 pin stereo plug.

Thanks

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73, Martin