SIM card locked to provider?

On Sat, 05 Jan 2008 09:01:55 GMT, Esther & Fester Bestertester
<[email protected]> wrote:

>A real basic question...
>
>If I buy a used AT&T GSM phone that is unlocked, do I need to buy a SIM card
>from T-Mobile if that is my carrier of choice? Or can the SIM be used for
>more than one carrier?
>
>In other words, when changing carriers, does one need to get a SIM card
>branded by the new carrier?

The SIM card is issued by the individual carrier, and allows the phone
to register with that carrier only.

Chris

---

› See More: SIM card locked to provider?

In <[email protected]> Chris Blunt <[email protected]> writes:
>>
>>In other words, when changing carriers, does one need to get a SIM card
>>branded by the new carrier?

>The SIM card is issued by the individual carrier, and allows the phone
>to register with that carrier only.

With the slight exception that many carriers have "roaming"
arrangements/partners, especially in areas where one
has coverage and the other doesn't.

But in general, you're best off, by far, in getting
the SIM issued by the carrier you want to use.

--
_____________________________________________________
Knowledge may be power, but communications is the key
[email protected]
[to foil spammers, my address has been double rot-13 encoded]

Esther & Fester Bestertester wrote:
> A real basic question...
>
> If I buy a used AT&T GSM phone that is unlocked, do I need to buy a SIM card
> from T-Mobile if that is my carrier of choice? Or can the SIM be used for
> more than one carrier?
>
> In other words, when changing carriers, does one need to get a SIM card
> branded by the new carrier?

SIM = Subscriber Identity Module. The required information for your
phone to request access is stored in the card, each time you turn the
phone on it attempts to register with networks within range. This is
only possible if it is the HOME network of your provider, or if there is
a roaming agreement with another network in range otherwise you will not
be able to make or receive calls.

Except 112 (standard GSM Emergency number), which is normally redirected
to the local Emergency number. If you are lucky the local Emergency
number is also mapped into the phone to work as 112. It is good
practice to dial 112 on a GSM phone as it flags the call as an EMERGENCY
call and will log into any network available and if required drop other
normal calls on that cell if required to initiate and maintain the
EMERGENCY call.


--
The views I present are that of my own and NOT of any organisation I may
belong to.

73 de Simon, VK3XEM.

["Followup-To:" header set to alt.cellular.]
On 2008-01-06, Simon Templar <[email protected]> wrote:


> Except 112 (standard GSM Emergency number), which is normally redirected
> to the local Emergency number. If you are lucky the local Emergency
> number is also mapped into the phone to work as 112. It is good
> practice to dial 112 on a GSM phone as it flags the call as an EMERGENCY
> call and will log into any network available and if required drop other
> normal calls on that cell if required to initiate and maintain the
> EMERGENCY call.

The OP was talking about T-Mobile and AT&T. AT&T is an American provider and
the Emergency number here is 911, not 112. I assume that since AT&T was
mentioned, the OP was talking about T-Mobile USA and not some overseas
division of T-Mobile.

Other than that, I agree with what you said.


--
Steve Sobol, Victorville, CA PGP:0xE3AE35ED www.SteveSobol.com
Geek-for-hire. Details: http://www.linkedin.com/in/stevesobol

On 2008-01-06, Steve Sobol <[email protected]> wrote:
> ["Followup-To:" header set to alt.cellular.]
> On 2008-01-06, Simon Templar <[email protected]> wrote:
>
>
>> Except 112 (standard GSM Emergency number), which is normally redirected
>> to the local Emergency number. If you are lucky the local Emergency
>> number is also mapped into the phone to work as 112. It is good
>> practice to dial 112 on a GSM phone as it flags the call as an EMERGENCY
>> call and will log into any network available and if required drop other
>> normal calls on that cell if required to initiate and maintain the
>> EMERGENCY call.
>
> The OP was talking about T-Mobile and AT&T. AT&T is an American provider and
> the Emergency number here is 911, not 112. I assume that since AT&T was
> mentioned, the OP was talking about T-Mobile USA and not some overseas
> division of T-Mobile.

Actually I'm pretty sure that 112 is a GSM standard emergency number,
and that dialing it should get you to the same place that 911 does in
the US and to whatever other number is used for emergencies in other
countries. Dialing 112 on my phone gets a message which asks if I
really want to make an emergency call on the AT&T network, so my
phone certainly seems to understand what it is.

Dennis Ferguson

In message <[email protected]> Steve Sobol
<[email protected]> wrote:

>["Followup-To:" header set to alt.cellular.]
>On 2008-01-06, Simon Templar <[email protected]> wrote:
>
>
>> Except 112 (standard GSM Emergency number), which is normally redirected
>> to the local Emergency number. If you are lucky the local Emergency
>> number is also mapped into the phone to work as 112. It is good
>> practice to dial 112 on a GSM phone as it flags the call as an EMERGENCY
>> call and will log into any network available and if required drop other
>> normal calls on that cell if required to initiate and maintain the
>> EMERGENCY call.
>
>The OP was talking about T-Mobile and AT&T. AT&T is an American provider and
>the Emergency number here is 911, not 112. I assume that since AT&T was
>mentioned, the OP was talking about T-Mobile USA and not some overseas
>division of T-Mobile.
>
>Other than that, I agree with what you said.

GSM still uses "112" internally. On US phones/SIMS (apologies, I don't
recall which does the translation), both 911 and 112 result in the call
getting flagged as "EMERGENCY"

The number dialed is irrelevant.

Steve Sobol wrote:

> ["Followup-To:" header set to alt.cellular.]
> On 2008-01-06, Simon Templar <[email protected]> wrote:
>
>
>> Except 112 (standard GSM Emergency number), which is normally
>> redirected to the local Emergency number. If you are lucky
>> the local Emergency umber is also mapped into the phone to
>> work as 112. It is good practice to dial 112 on a GSM phone
>> as it flags the call as an EMERGENCY call and will log into
>> any network available and if required drop other normal calls
>> on that cell if required to initiate and maintain the
>> EMERGENCY call.
>
> The OP was talking about T-Mobile and AT&T. AT&T is an
> American provider and the Emergency number here is 911, not
> 112. I assume that since AT&T was mentioned, the OP was
> talking about T-Mobile USA and not some overseas division of
> T-Mobile.

On a GSM phone, if dialling 911 provides the same functionality
as dialling 112, then that's because 911 is listed in the SIM's
EF_ECC (emergency call codes) file, at SIM address 6FB7.

John

On 2008-01-06, Dennis Ferguson <[email protected]> wrote:

> Actually I'm pretty sure that 112 is a GSM standard emergency number,
> and that dialing it should get you to the same place that 911 does in
> the US and to whatever other number is used for emergencies in other
> countries. Dialing 112 on my phone gets a message which asks if I
> really want to make an emergency call on the AT&T network, so my
> phone certainly seems to understand what it is.

911 is guaranteed to work, though; I've had to dial 911 on Verizon's network
and on T-Mobile's network, for example, and they both work fine. They'll work
fine on other US networks too. 112 may very well work on a GSM phone here,
but if you want to be sure you're dialing the emergency dispatcher, you dial
911.


--
Steve Sobol, Victorville, CA PGP:0xE3AE35ED www.SteveSobol.com
Geek-for-hire. Details: http://www.linkedin.com/in/stevesobol

In <[email protected]> Steve Sobol <[email protected]> writes:

>On 2008-01-06, Dennis Ferguson <[email protected]> wrote:

>> Actually I'm pretty sure that 112 is a GSM standard emergency number,
>> and that dialing it should get you to the same place that 911 does in
>> the US and to whatever other number is used for emergencies in other
>> countries. Dialing 112 on my phone gets a message which asks if I
>> really want to make an emergency call on the AT&T network, so my
>> phone certainly seems to understand what it is.

>911 is guaranteed to work, though; I've had to dial 911 on Verizon's network
>and on T-Mobile's network, for example, and they both work fine. They'll work
>fine on other US networks too. 112 may very well work on a GSM phone here,
>but if you want to be sure you're dialing the emergency dispatcher, you dial
>911.

All recent (?5 years?) GSM phones in the US will let
you call out to 911 and 112 (which gets translated
to 911) with or without a SIM, and whether or
not that SIM is activated. (Provided, of course,
that you're in radio range of a compatable GSM
base station).

I've also called out to "08". That one worked
with a SIM (and the call was routed to 911).
However, the phone did not "understand" that 08
was an emergency number, so didn't put it through
when I pulled out the SIM.

My phone is a few years old so I can't be sure
of what happens with the newest ones.

(And to those who need to get a life: In NYC when
there's a disabled vehicle on limited access highways,
the 911 PSAP is the notification point whether or
not there's an accident/injuries/fire, so I had
plenty of chances to make legitimate calls).


--
_____________________________________________________
Knowledge may be power, but communications is the key
[email protected]
[to foil spammers, my address has been double rot-13 encoded]

danny burstein wrote:

> All recent (?5 years?) GSM phones in the US will let
> you call out to 911 and 112 (which gets translated
> to 911) with or without a SIM, and whether or
> not that SIM is activated. (Provided, of course,
> that you're in radio range of a compatable GSM
> base station).

In the US, the translation will be from 911 to 112 (the GSM
distress-priority number) prior to the call being placed, and
then to 911 when the call hits the fixed telephone network.

Modern GSM phones will often have 911, 999 and 000 entered into
the SIM's EF_ECC file. So these and 112 will provide identical
functionality. You may be able to dial them and connect even
with the keypad locked.

John

Steve Sobol wrote:
> The OP was talking about T-Mobile and AT&T. AT&T is an American provider and
> the Emergency number here is 911, not 112. I assume that since AT&T was
> mentioned, the OP was talking about T-Mobile USA and not some overseas
> division of T-Mobile.
>
> Other than that, I agree with what you said.

112 is part of the GSM protocol and unless deliberately defeated by a
carrier is meant to work all over the world (provided you have access to
a network). The idea behind 112 was that no matter what country you
travelled to, you would not have to try and remember the local EMERGENCY
number.

As I said in my previous post, normally when a carrier sells a phone it
programmes the phone to dial 112 when you dial the local EMERGENCY
number but not always.

The GSM protocol also gives PRIORITY to 112 and will drop other calls on
the local cell to ensure the EMERGENCY call gets through.


--
The views I present are that of my own and NOT of any organisation I may
belong to.

73 de Simon, VK3XEM.

Simon Templar wrote:
> Esther & Fester Bestertester wrote:
>> A real basic question...
>>
>> If I buy a used AT&T GSM phone that is unlocked, do I need to buy a
>> SIM card from T-Mobile if that is my carrier of choice? Or can the SIM
>> be used for more than one carrier?
>> In other words, when changing carriers, does one need to get a SIM
>> card branded by the new carrier?
>
> SIM = Subscriber Identity Module. The required information for your
> phone to request access is stored in the card, each time you turn the
> phone on it attempts to register with networks within range. This is
> only possible if it is the HOME network of your provider, or if there is
> a roaming agreement with another network in range otherwise you will not
> be able to make or receive calls.
>
> Except 112 (standard GSM Emergency number), which is normally redirected
> to the local Emergency number. If you are lucky the local Emergency
> number is also mapped into the phone to work as 112. It is good
> practice to dial 112 on a GSM phone as it flags the call as an EMERGENCY
> call and will log into any network available and if required drop other
> normal calls on that cell if required to initiate and maintain the
> EMERGENCY call.


I'm unaware of any cell-based priority of 911 calls over any other call.
Certain IMEI codes can be assigned a higher access priority over other
IMEI codes, but this higher access priority would apply whether the
special IMEI handset called a hospital or the local crack dealer.


--
jer
email reply - I am not a 'ten'

Jer wrote:

> I'm unaware of any cell-based priority of 911 calls over any
> other call.
> Certain IMEI codes can be assigned a higher access priority
> over other IMEI codes, but this higher access priority would
> apply whether the special IMEI handset called a hospital or
> the local crack dealer.

In the more usual configuration, a phone of any access class can
make an emergency priority call. All that's required is that
the user dials 112 or a number in the SIM's EF_ECC file.

If there's no SIM fitted, then the handset itself might be able
to do an equivalent lookup of predefined emergency numbers in
firmware. So a call to 911 in a handset without a SIM _might_
be treated as an emergency call within the radio layer, and
connected with priority. Such a call will connect you to
emergency services however, rather than your prefered dealer.

While GSM 04.08 does allow for access to the emergency call
facility to be restricted to access classes 11 through 15, that
restriction is not normally in place.

John

"John Henderson" <[email protected]> wrote in message
news:[email protected]...
> Jer wrote:
>
>> I'm unaware of any cell-based priority of 911 calls over any
>> other call.
>> Certain IMEI codes can be assigned a higher access priority
>> over other IMEI codes, but this higher access priority would
>> apply whether the special IMEI handset called a hospital or
>> the local crack dealer.
>
> In the more usual configuration, a phone of any access class can
> make an emergency priority call. All that's required is that
> the user dials 112 or a number in the SIM's EF_ECC file.
>
> If there's no SIM fitted, then the handset itself might be able
> to do an equivalent lookup of predefined emergency numbers in
> firmware. So a call to 911 in a handset without a SIM _might_
> be treated as an emergency call within the radio layer, and
> connected with priority. Such a call will connect you to
> emergency services however, rather than your prefered dealer.
>
> While GSM 04.08 does allow for access to the emergency call
> facility to be restricted to access classes 11 through 15, that
> restriction is not normally in place.
>
> John
>
I guess some here don't know John Henderson or Simon Templar, if you have
heard something from somebody and these guys tell the opposite, you can be
sure you had heard incorrect info.

The GSM standard would map 112 as the emergency call number. My phone makes
an emergency call in the US when I dial 112 even if it comes from Europe.
Like explained, later enhancements allow 911 "calls" being interpreted
emergency calls. I guess it was mentioned that no number is delivered when
an emergency call is made, not even 112, the call is explicitly recognised
as an emergency call. An old phone in Europe might not make any emergency
call if you dial 911 but later ones would (you can try calling with your
keypad lock on, the phone would still accept emergency call numbers).

Also priority from IMEI would not work the way priority for emergency calls
works. The point being that the first channel request towards the network
would not have room for IMEI but does carry an indication about an emergency
call. The priority classes were already explained, being different from IMEI
priority (actually I'm not familiar with IMEI based call priority but am
neither claiming there could not be any).

Anonymous schrieb:
> [...] actually I'm not familiar with IMEI based call priority but am
> neither claiming there could not be any

What an IMEI based call priority system be good for? The IMEI is the
international mobile EQUIPMENT identifier, it tells the network
something about the UE beeing used (model and serial number). Now, why
would a network operator want to prioritize calls made with e.g. Samsung
phones over those from Nokia phones?

Andreas