Hello all!

Every time I go to fill up my car at a gas station I slide my card and enter my pin number into the little keypad on the pump. I have noticed that at a lot of stations, when you press a key on the keypad, the contrast on the LCD screen goes dim but the backlight stays lit as normal.

I was wondering if this is because of either poor grounding, or sharing some resistor between the keypad and LCD screen because of some kind of constraint.

It always seems weird that so many gas stations would use such a design that annoys the users since you can't read the screen every time you press the button.

Hope some of you guys with more experience might have an idea so that I won't make the same mistake!