LED

An output device.

An LED is a solid state (i.e. electronic) device that gives off a coloured light when a voltage is applied to it. Colour includes Red, Green, Blue, Orange, Yellow and White.

They are mainly used as indicator lights in equipment, for example the 'stand-by' or 'power-on' light in televisions etc.

The standard LED package is quite small (about 4mm across). An LED is very efficient compared to normal bulbs. They also last a long time - at least 100,000 hours (a bulb will last a few hundred hours)

The light is very pure, which is why LEDs are also used in low cost fibre-optic cable systems (high-cost systems use lasers)to transmit data.

Recently, low-cost high-power LEDs have been developed as a replacement for car indicators and brake lights. You will see many new cars sporting LED indicator lights.

All-in-all LEDs have proven to be very useful in a variety of indicator and signalling roles.