Very impressed with your responses throughout these 15 pages
@Terence
I understand how you cannot integrate the Trident with 10 year old hardware.
However, I am curious if there can be a module between older model Apex units and the Trident. Something that would convert the complex digital signal into something interpretable for classic units. Having worked with integrating new and old industrial hardware (particularly CNCs), I dont see why there could not be a microprocessor in between an Apex Classic and the Trident to make the results interpretable. Jim Welsh's design took minimal processing- cleverly he made the output the along the same voltage as a pH probe.
Anyway, I love where your products are going. I planned to get a 2016 Apex but had significant damage from Hurricane Irma that I am still paying off. So I am stuck with my Apex Lite for now

. Nevertheless I will keep following Neptune updates!