Yes. I actually fiddled with the same thing. My equipment uses a GSM radio, and everything bypasses the Android API. (do a stackoverflow search using the "[android] internal API" and you will get a ton of information on how to access it). In my case, I am interested in transmitting data via GSM. So, it is in the Android source code under /base/telephony/java/com/android/internal/telephony/DataConnectionTracker.java. If you are interested in other functions, such as SMS, SIM cards, voice calls or anything that is not available in the standard "public" API, look in the folder infrastructures / base / telephony / java / com / android / internal / telephony and the names are pretty important for what he does. As for the clear documentation, I did not find it. I think that it is not published, since it is not recommended to use internal APIs, because it can change without prior notice, and there is no guarantee that the internal API will not change in the next version of Android.