Hummer 2004 H2 - Manual (Page 221)

Rear Seat Audio (RSA)
This feature allows rear seat passengers to listen to any
of the audio sources: radio, cassette tapes, or CDs,
depending on your vehicles options. 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. The front seat audio controls always
override the RSA controls.
Rear Seat Audio Controls
The following functions are controlled by the RSA
system buttons:
P (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 unless your vehicle is
equipped with the Bose
® audio system. You may
operate the rear seat audio functions even when the
primary radio power is off.
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