Display systems required for
observing outputs from a device. Seven segment displays, an old type, is used
in calculators and some electronic devices. Usually a wiring pattern of LED
(Light emitting Diode) is used here by keeping one terminal as common. For
television systems, cathode ray tubes (CRTs) were used initially. A spot of
light is produced on the CRT screen which is coated with phosphor whenever
electron beam strikes it. Light emitting diodes are also used nowadays as
display systems. The basic principle employed here is electroluminance which is
the emission of light from a semiconductor under the influence of an electric
field. Liquid crystal display which is a low power consumption system employs a
thin layer of a liquid crystal cell
sandwiched between two glass sheets with transparent electrodes deposited on
their inside faces. The use of transparent glass sheets given this device
another name, transmittive type display. There are two categories in LCD
display. They are dynamic scattering display and field effect display. Cold
cathode display which is also known as Nixies works on the basis of emission of
light in a cold cathode gas filled tube under breakdown condition. Incandescent
displays which use the phenomenon incandescence is also giving promise as a
good display device for the future.
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