Question for people who understand SIM cards

[darwen]

I know this topic has been discussed a lot. It is my understanding that SIM cards can be swapped between phones, replacing a SIM card from Phone A with a card from Phone B allows all of the contacts and incoming calls from A to instead be on A. My question is this: does the phone know what SIM card is in it? What I mean is does it know what contract it is attached to.

Here is why I ask. I am thinking that Apple will just sell the phones and the SIM cards seperate in the stores. This way if you have a contract you can just buy the phone and pop your card in. If you don't you would need to buy a contract to get the card and have a working phone.

I know this has been discussed a lot. I am just curious though what current phones do... Would this be practical?

 

[bbplayer5]

Every phone needs to come with a sim chip. If you already have a chip, they wont give you a new one, they just keep it.

 

[cmschmidt]

the iphone will be locked to at&t. so unless you have at&t you won't be able use it. However, you more than likely won't just be able to buy an iphone without buying a contract. and the iphone will probably require a 64k sim instead of the 32k most people have.

 

[apfhex]

The SIM card contains your account/phone number, to put it simply, so whatever phone you put the card in with be using that account/number.

 

[cmschmidt]

The SIM card contains your account/phone number, to put it simply, so whatever phone you put the card in with be using that account/number.

in theory yes. but don't forget to mention that you can't just put any carriers sim into any carriers phone unless the phone is unlocked.

 

[r6girl]

when i've gotten new phones from cingular/at&t, i have gotten new sim cards from time to time, though i've never used them. any sim can be programmed to contain your account information. if you get a new sim with a phone and you want to switch to the new sim, i think all that's required is a call to your carrier so they can register the new sim with your account information. this may deactivate your old sim card, though.

also, a sim card can store contacts, but there's a memory limit so you may not be able to automatically transfer all of your contacts just using the sim. also, depending on the phone, you may need to specifically select to import/export contacts to and from your sim card. my treo 680, for example, automatically saves all contacts to the phone's memory only, and i have to choose to export contacts individually to the sim card. also, i had to choose to import contacts stored on the sim card to the phone's memory. and i've had other phone that automatically save contacts to the sim card only (mostly older phones). check the menus and features of your current phone to see what it can do about your contacts and what's saved on your sim card...

 

[darwen]

Ok, but lets say you walk into the Apple store with a SIM card conncted to an AT&T account on hand. Hypotheticly you could just have apple put the card in the iPhone and walk out withought signing any contracts, right?

I understand the price has been known to requre a 2 year contract and only certian contracts are going to be allowed on the phone (from several reports).

I am speaking hypotheticly though, is it possible for the phone to know from the SIM card what contract you have? Is that information stored in the card? Or is it accessible through the network from the information the card provides?

I am not trying to cheat the system, I am going to buy a phone and contract at purchase, I am just hypothosizing.

 

[cmschmidt]

assuming apple hasn't built anything into the phone requiring some special service (very unlikely), yes your normal sim will work just like any other phone.

 

[apfhex]

in theory yes. but don't forget to mention that you can't just put any carriers sim into any carriers phone unless the phone is unlocked.

Yes... I was assuming in this case that it would be an AT&T SIM and that they would let you use an existing one (provided you extended your contract) in a new iPhone, which may or may not be the case.

 

[darwen]

Thanks guys, good to hear.