12. LEDs

A Light Emitting Diode or LED is a semiconductor light source that emits visible light when charged with an electrical current.

LEDs are commonly integrated into many household appliances in order to provide you with information. This information is often to tell you whether an appliance is switched on or off, for example:

• televisions
• computers and monitors
• answer phones
• kettles
• clock radio alarms

They can also be used to indicate that something else has happened, for example:

• pressing the 'caps lock' button on your keyboard will light up the caps lock led
• flashing light on answer phone will indicate that a message has been received
• flashing light on burglar system to indicate that the system is active

As well as single LEDs being used in household appliances, technology has enabled them to be incorporated into information systems such as the examples below.

Electronic information display systems have been used for many years in places such as airports and train stations.

They generally consist of a large LED board either hanging from the ceiling or placed on the wall. The board displays basic details of all incoming and leaving flights/trains.

The board is updated regularly either by a person or automatically by software to ensure that the information displayed is correct and up-to-date.

As well as large boards such as the one above, single or multiple line LED message boards are now commonly being used to convey information and messages to the public.

They are also used a lot in companies where time matters! For example a call centre might display the average time people are waiting in the queue, which is meant to motivate the call centre staff to work faster!

As technology has moved on and prices have come down, LED information systems are commonly found in many public areas such as banks, hospitals, schools, cinemas and reception areas. Here are a few examples:

Hospital	Bank	School	G.P. Surgery

LEDs are even being used on the front of buses to display the bus number and route.

The technology works by using a series of dot matrix arrangements. The appropriate dot is lit up to display the required text message.

The LED outputs light which is much brighter than normal daylight or light bulbs. This makes it viewable in most conditions and locations.