All about IMEI

Structure of the IMEI and IMEISV

The IMEI (14 digits plus check digit) or IMEISV (16 digits) includes information on the origin, model, and serial number of the device. The structure of the IMEI/SV are specified in 3GPP TS 23.003. The model and origin comprise the initial 8-digit portion of the IMEI/SV, known as the Type Allocation Code (TAC). The remainder of the IMEI is manufacturer-defined, with a Luhn check digit at the end (which is never transmitted).
As of 2004, the format of the IMEI is AA-BBBBBB-CCCCCC-D, although it may not always be displayed this way. The IMEISV drops the Luhn check digit in favour of an additional 2 digits for the Software Version Number (SVN) in the format AA-BBBBBB-CCCCCC-EEAA BBBBBB CCCCCC D EEReporting Body Identifier, indicating the GSMA-approved group that allocated the model TAC The remainder of the TAC Serial sequence of the model Luhn check digit of the entire number (or zero) Software Version Number (SVN).
Prior to 2002, the TAC was 6 digits long and followed by a two-digit Final Assembly Code (FAC), which was a manufacturer-specific code indicating the location of the device's construction.

For example the IMEI code 35-209900-176148-1 or IMEISV code 35-209900-176148-23 tells us the following:TAC: 352099 so it was issued by the BABT and has the allocation number 2099FAC: 00 so it was numbered during the transition phase from the old format to the new format (described below)SNR: 176148 - uniquely identifying a unit of this modelCD: 1 so it is a GSM Phase 2 or higherSVN: 23 - The 'software version number' identifying the revision of the software installed on the phone. 99 is reserved.
The format changed from April 1, 2004 when the Final Assembly Code ceased to exist and the Type Approval Code increases to eight digits in length and became known as the Type Allocation Code. From January 1, 2003 until this time the FAC for all phones was 00.
The Reporting Body Identifier is allocated by the Global Decimal Administrator; the first two digits must be decimal (ie less than 0xA0) for it to be an IMEI and not an MEID.
The new CDMA Mobile Equipment Identifier (MEID) uses the same basic format as the IMEI.Retrieving IMEI information from a GSM device
On many devices the IMEI number can be retrieved by entering *#06#. The IMEI number of a GSM device can be retrieved by sending the command AT+CGSN. For more information refer the 3GPP TS 27.007, Section 5.4 /2/ standards document.
Retrieving IMEI Information from an Ericsson or Sony Ericsson handset can be done by entering these keys: Right * Left Left * Left * (Other service menu items will be presented with this key combination).

The IMEI information can be retrieved from most Nokia mobile phones by pressing *#92702689# (*#WAR0ANTY#), this opens the warranty menu in which the first item is the serial number (the IMEI). The warranty menu also shows other information such as the date the phone was made and the life timer of the phone.
The IMEI can frequently be displayed through phone menus, under a section titled 'System Information', 'Device', 'Phone Info' or similar. Many phones also have the IMEI listed on a label in the battery compartment.

IMEI and the law

Many countries have acknowledged the use of the IMEI in reducing the effect of mobile phone theft, which has increased exponentially over the last few years[citation needed]. For example, in the United Kingdom under the Mobile Telephones (Re-programming) Act, changing the IMEI of a phone, or possessing equipment that can change it, is considered an offence under some circumstances.
There is a misunderstanding amongst some regulators that the existence of a formally allocated IMEI number range to a GSM terminal implies that the terminal is approved or complies with regulatory requirements. This is not the case. The linkage between regulatory approval and IMEI allocation was removed in April 2000 with the introduction of the European R&TTE Directive. Since that date, IMEIs have been allocated by BABT (acting on behalf of the GSM Association) to legitimate GSM terminal manufacturers without the need to provide evidence of approval.
In Singapore, however, despite the high usage of mobile phones and the increasingly frequent cases of mobile phone theft, there is apparently no infrastructure available to "ban" the use of a stolen phone, given the IMEI. None of the local service providers seem to be aware of the IMEI or its use and most service providers believe that most phones still do not possess the technology to allow the service providers to "ban" the use of a stolen phone[citation needed].

Blacklist of stolen devices

When mobile equipment is stolen or lost, the operator or owner will typically contact the Central Equipment Identity Register (CEIR) which blacklists the device in all operator switches so that it will in effect become unusable, making theft of mobile equipment a useless business.
The IMEI number is not supposed to be easy to change, making the CEIR blacklisting effective. However this is not always the case: IMEI may be easy to change with special tools and operators may even flatly ignore the CEIR blacklist.
Difficulties
* "New IMEIs can be programmed into stolen handsets and 10% of IMEIs are not unique." According to a BT-Cellnet spokesman quoted by the BBC. [1]* Facilities do not exist to unblock numbers listed in error on all networks. This is possible in the UK, however, where the user who initially blocked the IMEI must quote a password chosen at the time the block was applied.


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