This standard, CTA-2020, specifies four Vertical Blanking Interval (VBI) waveforms in commercial use. The electrical properties of the waveforms are covered, but the meaning of the payload data is not. The waveforms apply to 525-line, interlaced (i.e. 480i) analog television signals. The waveforms may be present on analog inputs and analog outputs, but no conformance requirements about the actual presence of the waveforms are defined in CTA-2020.
