2005 GMC Sierra 1500 Pickup Owner's Manual - Page 288

Rear Seat Audio (RSA) This feature allows rear seat passengers to listen to any of the sources: radio, cassette tapes, CDs, or DVDs. However, the rear seat passengers can only control the sources that the front seat passengers are not listening to. For example, rear seat passengers may listen to and control cassette tapes, CDs, or DVDs through the 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 have priority over the RSA controls. If the front seat passengers switch the source for the main radio to a remote source, the RSA will not be able to control the source. You can operate the rear seat audio when the main radio is off. P (Power): Press this button to turn the 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. u (Volume): Turn this knob to increase or to decrease the volume. The left knob controls the left headphones and the right knob controls the right headphones. SRC (Source): Press this button to select a source: radio, cassette tapes, CDs, or DVDs. 3-122