On Thu, Dec 31, 2009 at 03:11:26PM -0500, Michael Muller wrote: > > Mark Wallace wrote: > > When my cell phone is turned off, it goes directly to voicemail without > > ringing the phone. This means that they have to scan their entire > > network for it in a second or two (I might be in New York or > > California). If what you say is true. > > I know very little about the mechanics of cellular, but I expect the way that > it works is there is some system that is recording the last tower to have > communicated with your phone. If no handshake has happened for a while, it > assumes your phone is off or unavailable. So it doesn't have to scan the > entire network, it just has to check a flag in a database.
Yes. The MSC contains the routing information needed to route a call or a SMS to a tower. As a user roams around between towers the network has to perform handoffs (google GSM / MSC / HLR for more GSM internals). The network knows the last tower you were connected to when you turn it off. > > It should be easy enough to test this: take the battery out of your phone and > see if there's any difference WRT the way that voicemail behaves. There isn't. > > I was also told by law enforcement that they can find a turned off cell > > phone if they try hard enough (It would have to be at the level of a > > missing person investigation, not a lost cell phone) > > Could you ask them how? I'd be very surprised if it's by virtue of some > communication feature of the cell phone. As Mike K pointed out, we wouldn't > be allowed to bring a cellphone on board a plane at all if it were able to > transmit while turned off. I agree. This sounds bogus. Evidence, please. > > A flash light battery left with the batteries in it will go dead because > > of the passive connection, we are talking about the turned off cell > > phone still doing something. This statement is self-contradictory. Comparing a "turned off flashlight" to a "turned off cellphone" is equal. Both are disabled circuits. Batteries will decay over time. Different types of batteries will decay at different rates. Dry chemical vs wet vs nimh vis lion vs lipo will all have different idle discharge rates. -m -- Mike Kershaw/Dragorn <[email protected]> GPG Fingerprint: 3546 89DF 3C9D ED80 3381 A661 D7B2 8822 738B BDB1 "This sick joke is my JOB!" -- Eric
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