Reading the manual, it appears to me that you need:
1. CO2 tank
2. Pressure regulator
3. Solenoid valve
4. Bubble counter with non-return valve (which I'm guessing is a fancy way of saying "back-flow" preventer valve)
5. External water flow in the form of a canister filter or power-head that pumps at a minimum of 1 liter/hour (Which doesn't seem like very much to me......)
It also appears that an optional item is an automatic PH tester, which, as near as I can tell, automatically regulates the flow of CO2 via the solenoid valve according to the PH of the water in your aquarium. (I'm not sure I understand this part too well.)
This device has everything to do with CO2 injection and, as far as I can tell, nothing directly to do with the regulation of any other substance in the tank.
If I've read this incorrectly, please forgive me because I don't know that much about CO2 injection and am in the process of learning.