Color killer
Encyclopedia
The color killer is an electronic stage in color TV receiver sets which acts as a muting circuit to cut off the color amplifiers when the TV receives a monochrome
signal.
When the frequencies of these signals equals the frequency of the color subcarrier wave, they may create an irritating color dot pattern like confetti, which interferes with the monochrome picture.
is transmitted along the back porch portion of the video signal. If the transmitted signal is monochromatic, then the burst is not transmitted. The color killer is actually a muting circuit in the chroma section which supervises the burst and turns off the color amplifiers if no burst is received (i.e. when the signal is received signal is monochromatic.)
and PAL
transmissions, the color TV signal can be represented as:
In this equation
and 
are attenuation factors, 
is the luminance
signal,
and 
are the so called color difference signals and 
is the angular frequency of the color carrier. 
is within the luminance bandwidth.
Monochrome
Monochrome describes paintings, drawings, design, or photographs in one color or shades of one color. A monochromatic object or image has colors in shades of limited colors or hues. Images using only shades of grey are called grayscale or black-and-white...
signal.
Monochromatic transmission
When a receiver is tuned to a monochrome transmission, the displayed scene should have no color components. However, there are two factors which result in color display even during monochrome transmission:- a high frequency component of the luminance signal
- a high frequency of external noise
When the frequencies of these signals equals the frequency of the color subcarrier wave, they may create an irritating color dot pattern like confetti, which interferes with the monochrome picture.
Color transmission
In a color TV waveform, a reference pulse, called the burstColorburst
Colorburst is a analog video, composite video signal generated by a video-signal generator used to keep the chrominance subcarrier synchronized in a color television signal...
is transmitted along the back porch portion of the video signal. If the transmitted signal is monochromatic, then the burst is not transmitted. The color killer is actually a muting circuit in the chroma section which supervises the burst and turns off the color amplifiers if no burst is received (i.e. when the signal is received signal is monochromatic.)
Equation
In NTSCNTSC
NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
and PAL
PAL
PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
transmissions, the color TV signal can be represented as:
In this equation
and are attenuation factors, is the luminanceLuminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle. The SI unit for luminance is candela per square...
signal,
and are the so called color difference signals and is the angular frequency of the color carrier. is within the luminance bandwidth.