Hello, I had asked the question elsewhere, but unfortunately I did not get an answer. It is about the antenna connections of the RCD 310. I have an RCD 310 in a Passat Mod. 2009, which had previously no radio installed and it works, at least I did not detect any malfunction. The speakers and the antenna were installed factory, including the connection cable with plugs. But for what are two single antenna connections installed in the vehicle, while on the RCD 310 a double connection One can only connect one of the existing plugs on the radio, which I did as well. I found an adapter when googled, which makes two single plugs a double plug. Had I had to install such an adapter and if, why? My first guess was that the second plug installed in the vehicle could be for radio devices with Navi, but why does the RCD 310 have a double plug, where it doesn’t have a Navi?