Editing Television (section)

====CRT====
{{main|Cathode-ray tube}}
[[File:Crt14.jpg|thumb|left|upright=0.9|A 14-inch cathode-ray tube showing its deflection coils and electron guns]]
The cathode-ray tube (CRT) is a [[vacuum tube]] containing one or more [[electron gun]]s (a source of [[electrons]] or electron emitter) and a [[fluorescent]] screen used to view images.<ref name="crthistory"/> It has the means to accelerate and deflect the electron beam(s) onto the screen to create the images. The images may represent electrical [[waveform]]s ([[oscilloscope]]), pictures (television, [[computer monitor]]), [[radar]] targets or others. The CRT uses an evacuated glass envelope that is large, deep (i.e., long from front screen face to rear end), fairly heavy, and relatively fragile. As a matter of safety, the face is typically made of thick [[lead glass]] so as to be highly shatter-resistant and to block most [[X-ray]] emissions, particularly if the CRT is used in a consumer product.

In television sets and [[computer monitor]]s, the entire front area of the tube is scanned repetitively and systematically in a fixed pattern called a [[raster scan|raster]]. An image is produced by controlling the intensity of each of the three [[electron beams]], one for each additive primary color (red, green, and blue) with a [[video signal]] as a reference.<ref name='workings'>{{cite web|title=How Computer Monitors Work|date=16 June 2000 |url=http://computer.howstuffworks.com/monitor7.htm |access-date=4 October 2009 }}</ref> In all modern CRT monitors and televisions, the beams are bent by ''magnetic deflection'', a varying magnetic field generated by coils and driven by electronic circuits around the neck of the tube, although [[electrostatic deflection]] is commonly used in [[oscilloscope]]s, a type of diagnostic instrument.<ref name='workings' />