Television

Commercially available since the late 1920s, the television set has become commonplace in homes, businesses and institutions, particularly as a vehicle for advertising, a source of entertainment, and news. Since the 1950s, television has been the main medium for molding public opinion.  Since the 1970s the availability of video cassettes, laserdiscs, DVDs and now Blu-ray Discs, have resulted in the television set frequently being used for viewing recorded as well as broadcast material. In recent years, Internet television has seen the rise of television available via the Internet through services such as iPlayer and Hulu.
Although other forms such as closed-circuit television (CCTV) are in use, the most common usage of the medium is for broadcast television, which was modeled on the existing radio broadcasting systems developed in the 1920s, and uses high-powered radio-frequency transmitters to broadcast the television signal to individual TV receivers.
The broadcast television system is typically disseminated via radio transmissions on designated channels in the 54–890 MHz frequency band. Signals are now often transmitted with stereo or surround sound in many countries. Until the 2000s broadcast TV programs were generally transmitted as an analog television signal, but during the decade several countries went almost exclusively digital.
A standard television set comprises multiple internal electronic circuits, including those for receiving and decoding broadcast signals. A visual display device which lacks a tuner is properly called a video monitor, rather than a television. A television system may use different technical standards such as digital television (DTV) and high-definition television (HDTV). Television systems are also used for surveillance, industrial process control, and guiding of weapons, in places where direct observation is difficult or dangerous. Some studies have found a link between infancy exposure to television and ADHD
Category:Everyday Objects