Speco Technologies CVC-6246IHR - Manual (Page 21)

① Press the SET button to display the SETUP menu and move the arrow
indicator to ‘AGC’ using the UP or DOWN button.
② SET ‘BACKLIGHT’ to the desired mode using the LEFT or RIGHT button.
▶HIGH ▶MIDDLE ▶LOW ▶OFF
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4) AUTO GAIN CONTROL (AGC)
AGC allows a brighter picture in low light conditions. Higher GAIN level
will yield a brighter screen but you might notice an increase in noise.