It exchanges the function of the Up Arrow button with the Down Arrow button.
With ASIAIR, it therefore controls whether you want AutoFocus to approach the focus point from a longer drawtube , or from a shorter drawtube.
Also, how can I tell what firmware came with the EAF (I just took delivery a week ago).
Run the EAF Firmware updater, which will tell you what firmware the connected EAF is currently running. Don't tell it to good adead if you don't want to use the latest firmware (at 3.3.5, at this moment).
Chen