Lock the mobile is also referred to SIM lock.A SIM lock, confused with PIN or PUK code, it is ability built-in to GSM phones by mobile phone companies. Network facilitators use this range to prevent the use of in these phones to fix countries and network providers.Now a days, phones can be locked to only give SIM cards from one or more of the following: • Countries (your phone will perform in the US, but not the UK) • Network facilitators (e.g. T-Mobile, Orange, etc) • Service facilitators (another name for network providers) • SIM kinds (i.e. Only special SIM cards can be used with the phone). Logically all mobile phones are shipped with country and network facilitator locks. More over, most recent phones have firmware installed on them which is special to the network facilitator. If you own a Cingular phone, it shows the Cingular logo and helps only Cingular characteristics. This firmware is installed by the program provider and is different from the locking mechanism. You can unlock a Cingular phone to perform with a T-Mobile network, but the phone will still show the Cingular logo and only facilities Cingular features.