about airpen

How they work
The airpen Pocket System uses the different speeds at which
light and sound travel to track the movement of its pen tip.

The digital pen emits infrared and ultrasonic signals as you write or draw. Its infrared and dual ultrasonic sensors, located in the memory unit, pick up the signals, and the pen then calculates the differences in arrival time between them to track tip movement. This is performed continuously, dozens of times a second, to provide a precise record of where the pen tip goes—and what you write or draw!