2003 Chevrolet Astro Owner's Manual - Page 166

Radio with CD SCV (Speed-Compensated Volume): With SCV, your audio system adjusts automatically to make up for road and wind noise as you drive. Set the volume at the desired level. Turn the control ring behind the upper knob clockwise to increase the SCV. Each notch on the control ring allows for more volume compensation at faster vehicle speeds. Then, as you drive, SCV automatically increases the volume, as necessary, to overcome noise at any speed. The volume level should always sound the same to you as you drive. If you don't want to use SCV, turn the control all the way down. Playing the Radio PWR (Power): Press this knob to turn the system on and off. VOL (Volume): Turn this knob to increase or to decrease volume. The knob is capable of rotating continuously. RECALL: Press this button to switch the display between the radio station frequency and the time. Time display is available with the ignition turned off. Finding a Station AM FM: Press this button to switch between AM, FM1 and FM2. The display will show your selection. TUNE: Press this knob lightly so it extends. Turn it to choose radio stations. Push the knob back into its stored position when you're not using it. 3-41