phase alternating line

(television)(PAL) The video signal format used in the UKPAL uses Amplitude Modulation for the video information, andFrequency Modulation for the audio information. The phaseof the colour subcarrier is reversed on alternate lineswhich (together with the use of a delay line) allows thereceiver to cancel any phase errors introduced in the pathbetween the studio and the end-user's receiver. Such phaseerrors are quite common and would cause the displayed coloursto shift in hue.

The US equivalent, NTSC, does not have this feature and thusrequires a user control to correct for transmission phaseerrors, hence the mis-expansion "Never Twice the Same Colour".

单词	phase alternating line
释义	DictionarySeepal phase alternating line phase alternating line (television)(PAL) The video signal format used in the UKPAL uses Amplitude Modulation for the video information, andFrequency Modulation for the audio information. The phaseof the colour subcarrier is reversed on alternate lineswhich (together with the use of a delay line) allows thereceiver to cancel any phase errors introduced in the pathbetween the studio and the end-user's receiver. Such phaseerrors are quite common and would cause the displayed coloursto shift in hue. The US equivalent, NTSC, does not have this feature and thusrequires a user control to correct for transmission phaseerrors, hence the mis-expansion "Never Twice the Same Colour". AcronymsSeePAL
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