| > But you can't just "turn off" cell tower associativity on your phone. That's what airplane mode does, because it's not good for the cell network if you can be heard by two base stations that share bands (and are normally too far away to interfere with each other) and easily happens when you have altitude. You can usually turn on WiFi/BT w/o exiting airplane mode, because lower-powered radio devices are typically permitted in situations that cell itself isn't. sim-less phones typically don't maintain association, because it costs battery to do so, and they only start talking to towers during an emergency call. However, there is no requirement one way or the other. The easiest way to tell is if the clock of a sim-less phone drifts over a month or two from something it was sync'd to, note that using GPS at all will often sync the clock, and some devices will "wake" the GPS module to allow it to keep an up-to-date almanac and tracking (the math kind, not the surveillance kind) parameters, so it is best to disable location entirely, instead of just avoiding using it. If the phone has been used for a long time with a reliable time source available (tower/gps/ntp/etc), it may have a pretty good drift calibration, so it may take quite some time for drift to be visible. |