Why does my iPhone send signals to the tower when it's off (and in airplane mode)? I can tell because I can hear the interference over my computer speakers. Anyone know?
You're a little confused about E911. If the iPhone had a GPS receiver then, yes, it very well could still be active in Airplane Mode but even A-GPS phones aren't going to transmit anything in Airplane Mode. That would make the mode useless. For the iPhone, E911 (that's the emergency service's equipment not the phone) uses tower-based location to find the phone through its GSM connection to the tower. If you're in Airplane Mode, all transmitting has been stopped thus preventing towers from locating the phone. That's the reason for Airplane Mode in the first place, so you're not transmitting anything on a plane.