2003 GMC Sierra 1500 Pickup Owner's Manual - Page 275

Rear Seat Audio (RSA) This feature allows rear seat passengers to listen to any of the audio sources: radio, cassette tapes, CDs, DVDs, XM (if your vehicle is equipped with XMTM Satellite Radio Service), or DAB (if your vehicle is equipped with DAB) 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: 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. 6 (Power): 3-120