A video signal level below which no light should be emitted from a TV screen (the level at which the screen is blanked); also, that portion of the time that a video signal is transmitted when it is at or below blanking. These time portions can be divided into a horizontal blanking interval (HBI) and a vertical blanking interval (VBI). Since no picture information is carried in either blanking interval in an NTSC signal, various ATV schemes propose using them for carrying augmentation information, such as higher quality sound or widescreen panel information. Potentially conflicting with those schemes are other schemes that already use the blanking intervals for descrambling codes, test transmission, time code, and test and reference signals. Reducing the duration of the blanking intervals to allow more picture information to be transmitted potentially conflicts with the demands of the scanning circuitry of older TV sets. Sometimes this conflict is said to be resolved by bezel coverage and overscanning.