GMC 2002 Yukon Denali Owner's Manual page 193

Rear Seat Audio Controls
The following functions are controlled by the RSA
system buttons:
PWR (Power): Press this button to turn the rear seat
audio system on or off. The rear speakers will be muted
when the power is turned on. You will hear your source
through headphones. You may operate the rear seat
audio functions even when the primary radio power
is off.
VOL (Volume): Press this knob lightly so it extends.
Turn the knob clockwise to increase volume and
counterclockwise to decrease volume. Push the knob
back into its stored position when you're not using it.
The upper knob controls the headphone plugged into the
upper jack and the lower knob controls the headphone
plugged into the lower jack.
AM FM: Press this button to switch between AM, FM1
and FM2. If the front passengers are already listening to
AM FM, the RSA controller will not switch between the
bands and cannot change the frequency.
Press AM FM to return to listening to the radio when a
cassette tape or CD is playing. The inactive tape or CD
will remain safely inside the radio for future listening.
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