The International Mobile Equipment Identity (or IMEI) is a unique number associated with every mobile phone. It is usually found behind the battery and can also be found by dialling *#06# into the phone.
The number is used by the GSM network to identify valid devices and therefore can be used to stop a stolen phone from accessing the network.
It is 15 digits long and broken up like nnnnnn-nn-nnnnnn-n. The first six digits are the the Type Approval Code that identifies where permission for that phone was first sought. The next two digits are the Final Assembly Code, which identify the company that manufactured the phone. The next six digits are the Serial Number and is unique to that phone. The last digit is a check digit. For Phase 1 phones this is a zero.
For example the code 352099-00-176148-1 tells use the following:
TAC: 352099 so it was approved in Finland (35) and has the approval number 2099
FAC: 00 so it was number during the transition phase from the old format to the new format (described below)
SNR: 176148
CD: 1 so it a GSM Phase 2 or higher
The format will change from the April 1, 2004 when the Final Assembly Code will no longer exist and the Type Approval Code will become eight digits in length and be known as the Type Allocation Code. From January 1, 2003 until this time the FAC for all phones will be 00.
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