GMC 2000 Envoy Owner's Manual page 154

Rear Seat Audio (RSA)
This feature allows rear seat passengers to listen to and
control any of the music sources, including AM
cassette tapes and CDs, through the Rear Seat Audio
(RSA) controller. However, the rear seat passengers
can only control the music sources that the front seat
passengers are not listening to. For example, rear seat
passengers may listen to a cassette tape through
headphones while the driver listens to the radio through
the front speakers. The rear seat passengers have control
of the volume for each set of headphones. Be aware that
the front seat audio controls always have priority over
the RSA controls. Note that if the front seat passengers
switch the source for the main radio to a remote source,
the RSA will play the same remote source. The rear
speakers will be muted when the RSA power is turned
on. You may operate the RSA functions even when the
main radio is off.
Note that this feature is intended for rear
seat passengers.
The following function is controlled by the knob on the
main radio:
-
PWR VOL: Push this knob twice to turn RSA off.
The following functions are controlled by the RSA
system buttons:
PWR: Press this button to turn RSA on or off.
-
FM,
VOL: 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 left VOL knob controls the left headphone and the
right VOL knob controls the right headphone.
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