From NCAA Rule Book
Basically, red LED lights worked so the offical(s) use this to determine the outcome. If the red LED lights DO NOT work, the offical(s) use the HORN to determine the outcome.
Section 7. Beginning and End of Period
Art. 1.
Each period shall begin when the ball becomes live.
Art. 2.
Each period shall end when the red light or LED lights have become
activated. When the light fails to operate or is not visible, each period shall
end with the sounding of the game-clock horn.
a. In games when the red light is not present, the game-clock horn shall
terminate players’ activity.
b. In games with a 10th-of-a-second game clock display and where an
official courtside monitor is used, the reading of zeros on the game
clock is to be used to determine whether a try for goal occurred
before or after the expiration of time in any period. When the game
clock is not visible, the officials shall verify the original call with
the use of the red/LED light(s). When the red/LED light(s) are not
visible, the sounding of the game-clock horn shall be utilized. When
definitive information is unattainable with the use of the monitor, the
original call stands.
http://www.ncaapublications.com/productdownloads/BR11.pdf
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