CITROEN DS3 Handbook page 346

05 USB PLAYER
Using the auxiliary input (AUX)
JAcK socket or USB port (according to vehicle)
The auxiliary input, JACK or USB, allows the connection of a
portable device (MP3 player...).
Do not connect a device to both the JACK socket and the USB
port at the same time.
Connect the portable device (MP3
player...) to the JACK socket or to
the USB port, using a suitable cable
(not supplied).
Press the SoURCE button several
times in succession and select AUX.
Adjusting the volume of the auxiliary
source
First adjust the volume of your portable device.
Then adjust the volume of your audio
system.
The display and control is via the portable device.