SIM card: What exactly is it for?

[DP]

I read about it the manual but my phone (Treo 650) seems to be doing everything it describes without a SIM card in it.

[davester]

The SIM card contains all of your account information. It's basically the ignition key for your phone, which cannot work as a phone without it. However, only GSM phones have SIM cards. If your carrier does not use GSM technology then your Treo will not connect to a GSM network (unless perhaps on "roam"?). Some phones are only capable of using one type of network (e.g. GSM, CDMA, iDEN, etc) whereas some have multiple different radio-wave encoding circuits and are therefore capable of communicating using several different methods. Sounds to me like that's what you have.

[Chupa Chupa]

If you have ATT/Cingular or T-Mob you have a SIM card as they use GSM. If you have Sprint or Verizon, their technology, CDMA, doesn't use SIM cards, which is why you don't have one.

[DP]

Thanx for the info. I have a Verizon phone that I bought off craigslist with no manual. My friend gave me his box with a manual and a SIM card in the box-he's with AT&T-so I was just curious.

[OWC Jamie]

I've taken the sim card out of my CDMA phone and swapped it with another one and I've never been able to figure out what was on the sim card, either. Certainly not stored numbers and my billing certainly didn't chenge..

[Mac1337]

Slip your SIM card into any unlocked phone and Bingo. SIM card decouples your handset from the provider.

[macphanatic]

billb - there is no sim card in a cdma phone. There may be a memory card depending on the phone.

The sim card holds account information, ie phone number, etc. It usually can hold contact names and numbers. How many it will hold depends on the chip. On gsm, you can switch the phone you use by merely moving the sim from one phone to another. (Doesn't always work, if you have a older sim and a newer phone). With CDMA you have to have your wireless company activate the phone you want to use.

Verizon world phones have a Vodafone sim chip that is only active when used outside the US and in countries that use GSM. Their world phones will not connect to gsm networks in the US.

[OWC Jamie]

:-)
my phone's kinda old.

GSP-1600
:-)

(and yes, until I shut the whole thing off a couple months ago I had all three services going on it)

agravating thing didn't work at all in the eastern half of the Med. :-)

[MGS_forgot_password]

Technically, it does not store you phone number. It stores a unique code called an IMSI. Your provider keeps a database called an HLR which maps the IMSI to your phone number.

[DP]

The slot will also take an SD card so if I need more storage I can use that.