An LED is commonly used as a "power on" indicator for many electronic devices. For the LED to produce discernible visible light in daylight, the forward-bias current needs to be in the moderate range ...

The small circuit shown here could act as a power indicator for the 230 V mains supply and in terms of efficiency is the equal of classical neon bulbs. Note first that the LED in this circuit flashes ...

This simple Mock Flasher LED simulates the indicator of a sophisticated Alarm system. It can be placed in doors, gates and vehicles to confuse intruders. The circuit is too simple using a Unijunction ...