Since its invention in the 1920s and popularization in the 1950s, the television set has been one of the most significant pieces of technology. While television technology has continued to evolve, many of the same principles have been employed by each generation of TV models even as programming has progressed from monochrome to color and from analog to digital delivery.
For a television to function, it must contain certain basic components. These include an input device such as an antenna for receiving a video signal, a tuner for interpreting the video signal and distinguishing signals and a screen for displaying images. Most televisions also contain signal outputs for connecting external speakers or recording devices and a control interface for viewers to alter volume, change channels and calibrate the quality of the image.
The earliest televisions were based on radio technology with the addition of an image component. Modern televisions were born in the early 1900s with the development of the cathode-ray tube, a vacuum tube consisting of an electron gun and a screen. Cathode-ray tubes rely on electromagnets and the precise control of electrical currents. In the 1950s, the coaxial F connector was another important step in television development, allowing for the connection of an external antenna and, eventually, connection to cable or satellite delivery.
Each of a television's components serves an essential function. Cathode-ray tubes project a stream of electrons that are bent by an electromagnetic coil before striking the screen. On the surface of the screen, these electrons are interpreted as colors, which blend together to produce the image. The order and sequence of the electrons emitted by the electron gun are determined by the tuner, which uses a series of circuits to isolate an input signal. The tuner also transmits audio information to the speakers.
Since televisions became common in the 1950s, components have continued to be refined. Most televisions no longer contain cathode-ray tubes. Instead, a matrix of electrical circuits send color information to a series of plasma cells or liquid crystal pixels. These technologies are the basis for the modern plasma and LCD television sets, respectively. Television controls have evolved from dials that resembled radio tuners to remote controls that use infrared or short-range radio signals to allow viewers to operate a television from a distance.
As a complex system,a television and its components are subject to a number of problems. Cathode-ray tubes wear out and image quality naturally deteriorates. Newer screen types also are subject to problems. LCD screens can suffer electrical glitches that result in permanently lit or permanently dark pixels. Plasma screens are prone to screen burn, in which an image can become permanently etched into the screen if it is displayed for a long time. While those problems may be impossible to repair, loose electrical connections and blown-out speakers are common problems that can be resolved easily by a repair technician.