Active capacitive pen. When we talk about pens and styluses, we typically discuss two types: Electromagnetic and capacitive (which is more rightly called passive capacitive), where the former is superior and the latter is no better than using your finger. Surface Pen is a third type, called an active capacitive pen, and is similar to the technology used on Microsoft's Perceptive Pixel displays. An active capacitive pen requires batteries—see below—but in trade you get much better precision ("parallax"), consistent and accurate pressure sensitivity, more buttons, and excellent palm detection, among other improvements.