This information is already out there, take a look at the product page on our website. The dosing pump that is already assigned as the ALK pump is controlled by the KHD. You do not need yet another ALK dosing pump.Under normal conditions, the dosing schedule you set will run, but if a test comes back with a KH value below the desired value, KHD will tell the assigned pump to dose in addition to the regular dosing schedule.
You can also find more information on how it works, by taking a look at a recent AquaNerd post:
http://aquanerd.com/2017/08/ghl-to-release-kh-director-to-monitor-and-dose-alk.html
There's also a video posted by Reefwiser with information on page 6.
Additional info will be released soon.
And what happens if the test value comes above the desired value...? I presume... nothing? Not much control than...