JohnO wrote:

Last I checked, some stations put color bars on one line, multiburst on
another, and some other patters on other lines. These are useless for
display, but perfect for checking signal performance with vectorscopes and
waveform monitors. Otherwise, those lines are wasted space.

It's called VITS, Vertical Interval Test Signals

From the Grass Valley Dictionary:

VITS - A signal that may be included during the vertical blanking
interval to permit on-the-air testing of video circuit functions
and adjustments.

Other data that may be encoded in the vertical interval are closed captioning,
VIRS, Vertical Interval Reference Signals, and VITC, Vertical Interval TimeCode,
which is encoded SMPTE timecode data.

--
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Michael Kesti | "And like, one and one don't make
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mrkesti at comcast dot net | - The Who, Bargain