The 3mm breathing / fading round top red LED will automatically start fading / breathing once it is appropriately hooked up to power. The fading/breathing LED will slowly turn on and then slowly or gradually turn off in a similar manner to a standby light on a laptop or other types of computers/electronics. There is nothing extra needed when hooking this led up to power. A power source led, and resistor is all you need.

Specifications:

Size 3mm Round Top Fading / Breathing / Pulsing LED Color Red Animation Type Fading / Breathing Style Luminosity/Brightness 6,000-8,000 mcd Forward Voltage 1.9-2.1v Current 20mA Wavelength 620-630nm Viewing Angle 20-30 Degrees Mount Style Through Hole (DIP) Lens Color Clear LED Brightness Class Super/Ultra/Extreme"