MILKey: multi illuminated indicator for KEYpad

An indicator with switchable faces that suits the cellular phone keypad is proposed and implemented. The prototype, which can show 3 patterns, consists of notch filters (each of which yields a different pattern) and light sources. Each pattern, which emits in a different color, can be activated simply by switching the same color of the illuminating light. Since the patterns do not disturb each other, large characters can be covered on the whole keytop. This indicator is also suitable for handheld/portable devices, such as PDA or notebook PC.