Curious question here. I noticed that most, if not all generic/not original flip covers doesn't work on my smartphone. I have a lenovo phone that comes with a free flip cover. I bought a generic flip cover but I was disappointed to learn that the screen doesn't turn on/off the screen when I open/close the flip cover. The same thing i noticed on my wife's S4.
How exactly does original flip covers work and what is it equipped with that is missing on generic stuff?