USB SD AUX MP3 Adaptor and Bluetooth Hands-Free System for RD4, RT3 , RT4 Radio for the Following Models: Citroen: C2, C3 , C4 , C5, C6, C8, Berlingo, Jumpy / Peugeot:
AudioPro | Steinberg Ur-rt4 | 4-channel Usb 2.0 Audio Interface With 4 Rupert Neve Transformers
Citroen C5 How to connect your phone to RT4 radio, RT5 - YouTube
Steinberg UR-RT4 USB Audio Interface with 4 Rupert Neve Transformers | Sweetwater