You can use another audio device, such as a portable digital music player, with your system. This requires using a stereo audio cable with a 3.5 mm (1/8-inch) mini plug (not provided) that is appropriate for the connected audio device that plugs into the AUDIO INPUT connector on the back of the SoundDock® system.
Insert the audio cable from your audio device into the AUDIO INPUT jack on the back of the SoundDock® system. If your iPod® or iPhone® is not docked, the connected device will play automatically once it sends an audio signal to the SoundDock® system
Set the connected device to full volume, and then use the SoundDock® system volume buttons to adjust the level
On the SoundDock® remote press and hold PLAY/PAUSE for three to five seconds to enable the connected device to play through the system if your iPod® or iPhone® is charging in the dock.
The iPod® or iPhone® charges while you are playing audio from the connected device
On the remote, press and release PLAY/PAUSE to switch from the connected device to your docked iPod or iPhone.