“We all love our modern devices ranging from smartphones to smart cars and all of it is made possible thanks to the transistor! The technology we use has only been around for a few decades, so how did engineers in the past create complex digital circuits? This also brings up the question “how did NASA build a computer that was small enough to fit on the Apollo modules?” The answer lies in RTL which stands for resistor-transistor logic which for a while was one of the most popular logic families.”