I owe a Citroen Berlingo 2002, problem is no audio in.
The result is a 3.5mm female jack getting out the radio. So when you want to listen to music, set the volume of the radio down to minimum, connect your mp3 player (phone, ipod, etc.) and click play!
We need to remove and disassemble the radio and make 4 little weldings in it. We will use an audio 3.5mm female jack cable (but you can use whatever sound interface you like - es. male 3,5mm jack, female-male 6,3mm jack, female/male RCA audio - )
The VDO RD3-00 is a car radio sold with other cars by Citroen/Peugeot:
Citroen Xara Picasso
I did get the info for the welding from this article
, but didn't understood anything else because it is written in Spanish, I think!