Iphone 3G read one time of IMSI when validate SIM card is whether effective net-work provider’s simcard, won’t read card anymore after that. But send the read IMSI of validating to signal transmission spot to validate directly. This will result in no signal, as iPhone 3g / GSM’s IMSI is not legal.

     But why we can make it workable? Because we have some common mobile phones to let the SIM card gain a effective TMSI before this, then when iPhone 3G phone reading card, it will make the net-work provider (such as AT&T) of the sim unlock card’s IMSI and SIM card’s TMSI read it to mobile phone though IMSI is not effective after validate. But TMSI is effective, so we can use the iPhone 3G. But there is one point, TMSI will be disabled,(when changing signal transmission spot), after invalidated or be about to invalidate, signal transmission spot will require validate IMSI. In this way, it can send new TMSI to mobile phone. To solve this problem only to have some common mobile phones again to gain effective TMST, that is to say to put the SIM card to common mobile iPhone to gain signal when power on via signal transmission spot. Then put SIM card return to iPhone 3g phone, so can gain effective TMST, win normal use effect.The Iphone 3G reads the IMSI only one time when validating the network providers simcard. After that the Sim Card isnt read again. This causes problems when traveling out of one cell towers range and into another. When being passed to another cell tower there will be a loss of signal. The signal is permanently lost. The only way to recover the signal is to remove the Sim card and place it into another phone. This will cause the IMSI to be read again. You would then remove the sim card and place it back into the Iphone 3G. This will reset the process and effectively regain the signal that was lost. This process needs to be repeated if encountering a new cell tower quadrant. Unfortunately this is currently the only solution for the Iphone 3G.`

NEW NO CUTTING SIMCARD  FOR iPhone 3G V2.2 AND V2.2.1----ZCGH TURBOSIM(GHX-878)

 Features:
This version Renews Network Key Automatically with ZCGH TURBOSIM  Advanced IMSI handling & instant renewal on all operator networks, NO NEED to take out your simcard anymore to renew Network key..
- Support for iPhone 3G firmware 2.2.1
- Support for iPhone Modem firmware 02.30.03
- Advanced IMSI handling & instant renewal on all operator networks. Renews Network Key Automaticaly.
- Support for iTunes on iPhone in 3G mode without WiFi.
- Support for Apps Store on 3G, without WiFi.
- No iTunes Sync or Airplane mode issues.
- GPRS/EDGE & Voice support for all 2G networks worldwide.
- Data & Voice for 90%+ 3G Networks worldwide.
- Network Operator STK menu support.
- Network Access routines improved and rewritten.
- Simcard Access routines improved, will now support more network simcards.

more information : http://www.i-smartphone2008.com/si/products_show.asp?key=287