Colour TV system including auxiliary information - replaces colour subcarrier burst on some lines by burst of different frequency

摘要

The colour television system, such as the NTSC system transmits at least a part of the chromatic information as suppressed carrier amplitude modulation of a subcarrier. A subcarrier burst is inserted in the signal as a reference signal for use in demodulating the signal. The subcarrier bursts are suppressed from some of the lines of the TV signal and replaced by signals carrying additional sound or picture information such as emergency messages, newsflashes or the like. The bursts may be suppressed on alternate lines. The additional information may be carried as a burst at a frequency different from the subcarrier frequency.