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Topic: Multiple SIM Cards

yardie
Member

Registered: Feb 2000
Location:
Posts: 1571

Multiple SIM Cards

Is it possible to have more than one SIM Card with the same phone number? I call my provider and they say that it was not possible. I am not convinced though.

12-20-2001 10:47 AM

Travis
Member

Registered: Jun 2000
Location: Nashville, TN USA
Posts: 125

I'm sure it's possible, but not easy.
Actually, it's probably easy if you have the equipment.
What you would have to do is reprogram the second sim card to have the same ID as the first.

That way your cellphone & your visorphone would both ring or you could use either one. You would get into a problem if both you and someone else tried to use the phones at the same time.

I believe this whole procedure is called cloning.

Sorry, I've never done it so I don't know the particulars - I'm sure a web search would probably lead you to some "gray" sites with information.

Good luck and let us know if it works. I've got an extra sim card laying around and now you've got me thinking!!!!

Things that make you go hmmmmmmm

Travis

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12-20-2001 02:16 PM

nwhitfield
Member

Registered: Feb 2000
Location: London, UK
Posts: 92

Re: Multiple SIM Cards

quote:
Originally posted by yardie
Is it possible to have more than one SIM Card with the same phone number? I call my provider and they say that it was not possible.

Yep, of course it's possible. You don't need clone cards, either.

You have a second SIM with the same phone number (but a different SIM number, which is what GSM actually looks for to make the phone ring - that's how you can, for example, get a SIM update via SMS to change your phone number, as when the UK mobile codes changed).

Not all networks offer this; for example, in the UK the only one that does is Vodafone. But when it's set up, the network will try each SIM in turn when a call arrives for your particular number, and stop when the first phone responds.

So, if you have a car radio with a GSM SIM slot (some Blaupunkt models do, for instance) and a matched SIM for your mobile, you'd typically put the first searched for SIM in the car unit. Then when you get in the car and have the radio/GSM unit turned on, the network (via the Location Registers that track SIMs) will find that first, and all your calls will come through on the hands free, even if your mobile is turned on.

Stop the car, turn it off, radio switches off, and the calls will automatically end up on your mobile again, without you having to do anything messy like switching diverts on and off.

Similarly, if you had a second SIM in your VP or Treo, you turn on the phone section of that when you want to use it and it could override your mobile (or the other way round, depnding on which SIM you put in which device).

If your network says it can't be done, they're a) wrong and b) the staff probably think it can't be done because it's not a service that they offer.

Nigel.

12-20-2001 03:00 PM

yardie
Member

Registered: Feb 2000
Location:
Posts: 1571

Setup

OK NWhitfied.

Since you appear to be the GSM phone guru on these boards...how would I setup this up? Is it possible for me to get a generic SIM card and set it up some how? I know that I will not be getting any help from my cell phone provider because they insist that each SIM card has its own phone number so I cannot use multiple SIMs with the same number.

Please let me know where to start. The switching of SIM cards between the VPhone and my Ericcson is becoming a pain. The card is not easily removed from the Ericcson T28. I am in Canada BTW.

12-20-2001 11:30 PM

nwhitfield
Member

Registered: Feb 2000
Location: London, UK
Posts: 92

Re: Setup

quote:
Originally posted by yardie
how would I setup this up? Is it possible for me to get a generic SIM card and set it up some how?

My gut feeling on this is that it's not going to be something that's going to be easy (if possible) to do yourself.

Unlike other cellphone systems, in GSM the number isn't hard coded into the phone, as you know. It is usually stored on the SIM, but not necessarily - you'll sometimes pick up a phone that doesn't appear to know its own number.

That's because it's not actually necessary; the phone number is not used to deliver a call to the mobile. Instead, the network (via its Home Location Register and other means) keeps a record of which SIM corresponds to which number. When a call arrives, a message is sent to a particular SIM, each of which has a unique serial number. So in the dual SIM case I mentioned, the network is storing a list of SIM serial numbers to try - and that obviously means the network has to be configured to do that, which is something you have no control over.

Cloning of SIMs is pretty hard in GSM, though I gather it can be done, with the right equipment. It's certainly much easier with other non-smart card systems. But if you do that, you'll have two SIMs with the same serial number, installed in different pieces of equipment at the same time. Each GSM terminal (PDA, mobile, PC card, etc) has an IMEI number, which is unique, and also sent to the network during sign on.

If you were able to find someone to clone a SIM, I can't see how turning on two devices, thereby telling the network that the same SIM is being used simultaneously in two different pieces of equipment (since it would get two IMEIs as well) is going to avoid triggering any anti-fraud systems, unless your network is really sloppy about that kind of thing.

So, I'm afraid that if your network is not supporting multi-sim operation, there's not a solution for you, unless you want to run the risk of being accused of fraud, even assuming you could sufficiently reprogram a SIM card to have the same serial number as your existing one.

Sorry,

Nigel.

12-22-2001 11:43 AM

Brian812
Member

Registered: Jan 2001
Location: Arlington TX
Posts: 67

Now you are going to make me talk to my cell provider again. I have a T-28 as well as a VP and I am tired of flipping the SIM lets see if I can get two with the same number

01-18-2002 04:37 PM

timbond
Member

Registered: Jan 2002
Location: Augusta, Georgia, USA
Posts: 15

quote:
Originally posted by Brian812
Now you are going to make me talk to my cell provider again. I have a T-28 as well as a VP and I am tired of flipping the SIM lets see if I can get two with the same number

If that provider is VoiceStream, I really don't imagine you'll have much (if any) success. Heck, they don't even think it is possible to have two phone numbers on one SIM (funny, Powertel did it just fine before VS took over....), so something that comes off as "cloning" would just be too darned scary for them.

Of course, now I want the SIM-capable car radio that Nwhitfield mentioned. That only makes perfect sense...

01-18-2002 09:07 PM

Brian812
Member

Registered: Jan 2001
Location: Arlington TX
Posts: 67

Depends on the day of the week

Yes it is VS and in the past when I have talked with them one day they say I can do it and the next they are not sure. I think it just depends on who you get when you call their 800 number. I will have to ask about the two phone numbers on one sim as well. That way I would not have to carry two phones.

Oh and yes that radio sounds like a good idea as well

01-20-2002 03:59 PM

nwhitfield
Member

Registered: Feb 2000
Location: London, UK
Posts: 92

Re: Depends on the day of the week

quote:
Originally posted by Brian812
I will have to ask about the two phone numbers on one sim as well. That way I would not have to carry two phones.

The technical name for it is ALS - Alternate Line Service. Some providers call it "Line 2," and lots of others just don't bother offering it.

The Blaupunkt radio/GSM unit I mentioned is (having managed to track it down on their web site) the Antares T60, but I can't find an english page with the details, I'm afraid.

Nigel

01-21-2002 12:04 AM

Brian812
Member

Registered: Jan 2001
Location: Arlington TX
Posts: 67

Nigel,

You sure seem to be a man in the know. I will have to keep looking for the radio and the english site when it is up. I do believe VoiceStream does offer the ALS that you talk about though I have not had time to check up on it yet.

01-22-2002 08:35 PM

timbond
Member

Registered: Jan 2002
Location: Augusta, Georgia, USA
Posts: 15

quote:
Originally posted by Brian812
Nigel,

You sure seem to be a man in the know. I will have to keep looking for the radio and the english site when it is up. I do believe VoiceStream does offer the ALS that you talk about though I have not had time to check up on it yet.

Brian,

I have tried to get VoiceStream here in Georgia to provide a second line on my phone since last fall when they simply removed the second line I already had with Powertel (yes, even without telling me that people calling that number would suddenly get a recording saying that number wasn't assigned). I was told that VoiceStream did not offer that feature, so they had to remove it during the merger.

After that, anytime I asked I was basically told it was impossible to have two numbers on one SIM. If you have any success with that, I'd really like to hear about it.

As for carrying two phones, I just had one number always forwarded to the phone I carry. That, of course, doubles the minutes, but that second number was so infrequently used it didn't make a difference.

01-22-2002 08:57 PM

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