GSM detection/identification

Paul Buede paul at
Thu Jul 31 02:38:58 CEST 2008

ian douglas wrote:
> Paul Buede wrote:
>> the coverage isn't great in the rural areas I find myself.  When driving
>> around, if out of reach of tmobile, it will say "registering" as if
>> there is no sim card.  But, on the little image of the antenna, that
>> shows how strong my connection is, I still have 2 bars.  Is that a bad
>> guage of connectivity?
> As far as I recall, TMobile only uses the higher-frequency band, (1800
> or 1900? I can never remember), and probably won't drop down to the
> 850MHz band unless they've signed an agreement with AT&T to piggyback on
> their lower-frequency network in the rural areas where you've been.
> -id

Anybody else know what I can query or run to view available cell
carriers at any given time?  Is this even possible?  Correct me if I am
wrong, I am kind of making this up to try and figure out how it works:

Phone with no SIM card listens and transmits on given frequency, in
Neo's case its 1800/1900 and 850 in the US.  I assume it can see all the
various cell carriers, but cannot "register" until it has the SIM card,
which acts as a key, maybe analogous to a public key?  Once it has that,
it can register with the provider, and the provider queries its systems
to see if the SIM has an account associated, and if so what level of
service is associated with the SIM. 

Under my completely made up scenario, without a SIM I ought to be able
to see the various carriers who respond to queries, but who I cannot
register with, due to my lack of their public key (probably a bad
analogy, but its all I have right now).

Thanks, and please enlighten me.

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