Environmental controllers

I am wondering how an environmental controller such as the Sentinel Basic Environmental Controller works? From my understanding, you plug your inline fan into the controller and it controls the speed. How would you be able to control temp and humidity at the same time which this unit says it does?

It has a remote sensor that reads whatever the controller is designed for. ie. temp, co2, or RH. For example, their BTC-1 controls temp. You set the temp, set the deadzone, and it will activate your fan when the temp exceeds what you set it to (minus the deadzone). Not much else to say about them. You need to get a separate fan speed controller to adjust the speed of your inline fan.

EDIT: Sorry, I confused the Sentinel with a Blue Print version that I have in the mom's room. The Sentinel does not have an adjustable deadzone.