Yamaha YAS-CU207 Owner's Manual page 27

7
DIMMER key
Change the brightness of the indicators. Each time the key is
pressed, the brightness of the indicators changes as follows.
Dim (default setting) → Off → Bright
↑
Indicators glow brightly just after operation and change to the
specified brightness after a few seconds.
Decoder indicator
The unit supports the following audio signals. The color of the
indicator identifies the type of audio input signal.
Green (Dolby Digital), Red (DTS)
Off (PCM/analog signal/no input signal)
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