Pontiac 2003 Montana Owner's Manual page 271

Rear Seat Audio (RSA) (Without
Rear Seat Radio Controls
Primary Radio Controls
The following function is controlled by the knob on the
main radio:
PWR (Power): Push this knob twice to turn RSA off.
The following functions are controlled by the RSA
system buttons:
PWR (Power): Press this button to turn RSA on or off.
VOL (Volume): Press this knob lightly so it extends.
Turn the knob to increase or to decrease volume. Push
the knob back into its stored position when you're
not using it. The upper VOL knob controls the upper
headphone and the lower VOL knob controls the lower
headphone.
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