I have bought many iPhone 4 cables, mostly from amazon (where they are labelled "certified by Apple USB cable for APPLE iPhone 4/4s, ..."); with some of them the iPhone "bings" and starts loading, with others nothing happens. It seems to have to do with the source, but not always. For example, I have ports on my notebook, with some cables the iPhone starts loading, with others nothing happens. I have purchased a new iPhone 4 cable at amazon, it works when loading from the wall socket via a certified converter, but not when connected to the notebook. A few work fine everywhere, but at some point the cable begins to cause connection problems due to breakage from bending. I live near Frankfurt, Germany. The question: Is there a reliable international source for purchasing cables which are supported and should always function?