Text 247, 80 rader
Skriven 2004-08-01 00:46:01 av Michiel van der Vlist (2:280/5555)
    Kommentar till text 185 av Robert Bashe (2:2448/44)
Ärende: Fido on the move via cell phone.
========================================
Hi Bob,

 > [SIM card]
 > RB>> The only time you replace it is if you want to change providers
 > RB>> or want a new telephone number.

Actuallly there is no technical need to change the SIM card fo r a change of
telephone number. The telephone number is not on the SIM. The SIM contains the
IMSI. The link between the IMSI and the phone number is in the provider's Home
Location Registry. The phone number can be schanged by editing the HLR. Not all
providers offer that service though...

 > PK> .... or to upgrade to new features, or to replace a lost card.

 > Upgrade?

From 8K to 32K memory?

 > Not that I'm aware. You really do have to buy a
 > new phone for that, since it's generally even impossible to
 > flash new firmware (the flash RAMs are intentionally made
 > incompatible from model to model to prevent a cheap phone
 > from being upgraded to a more expensive one). And to
 > replace a "lost" card? How would you lose the SIM card in a
 > mobile phone without losing the phone too?

By having two SIM's for different providers one phone?

 > A SIM card doesn't just "fall out" of the phone, since it's in some
 > kind of socket in the phone's interior.

That indeed is unlikely, but some people frequently travel between two
countries and they have a SIM card for each country.

As for upgrades: I once had my SIM replaced by a so called dual card. A dual
card is two SIM's with the same IMSI. My old phone (Sony CMD-X2000) became
unstable for shirt pocket use but still worked fine in the car kit. I got
myself a SIEMENS M35 for regular use.

So instead of getting a new car kit, I got myself a dual card. One card is in
the old phone that remains in the car, in the car kit, and the other card is in
the "handy".


So instead of having to swap the SIM card, I just switch off the "handy" when I
take the car. The phone in th ecar comes on when I switch on the ignition.

I should add that car kits are compulsory when using a phone while driving in
The Netherlands.

 > I guess I'll have to accept that, although it seems
 > astounding to me - poor Japanese telephone customers! Just
 > imagine the screams of anger if something like that - where
 > you have no choice of provider but are forced to use the
 > specific one your phone is set to -  were to be introduced
 > in Europe. The prepaid packages here often try to do that -
 > the phone's firmware is set so that it only accepts the SIM
 > card of a specific provider, the one that subsidizes the
 > cost of the phone - but there are ways of hacking the
 > firmware to remove that restriction,

yes, the so called SIM lock. Originally meant as a deterrenty t theft, it was
used by providers to discourage changing providers. here in The Netherlands
providers were bound by law to supply the unlock code for free after one year.

In the meantime the practise has vanished. One can now buy "naked" SIM lock
free phones.

 > and this is often done (it's even legal to do so in the
 > Netherlands, where people offfer this service).

Indeed it is. Or if one has enough courage one can hunt the web for the rquired
software, get a "data cable" and do it oneself. I had my Siemens M35 unlocked
that way. Didn't want to wait a year. I needed the data cable anyway to
interface it to my laptop.

Cheers, Michiel

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