Although SIM card holds many different types of information but the part which involves carrier unlock is the IMSI number. IMSI (International Mobile Subscriber Identity) is a unique number that corresponds to your account in the mobile carrier’s database. Every IMSI number consists of a MCC (Mobile Country Code) and MNC (Mobile Network Code). Example [...]

UPDATE 1: Apple is fast this time. iOS 5.0.1 is no longer being signed. Baseband downgrade to 4.11.08 is no longer possible. First : This tutorial will be valid for as long as Apple is still signing iOS 5.0.1. Once Apple stops signing iOS 5.0.1, you can no longer downgrade your baseband to 4.11.08. You [...]

If you have an iPhone3GS and if digits 3-5 of its Serial Number are 134 or later (xx134…), then you should NOT try to install the 06.15 baseband on your 3GS! It will brick your radio, preventing both the downgrade from working and normal iPhone software from using it as a phone! Be warned! Step [...]