Story behind IMEI number !
GSM Association IMEI Allocation and Approval Guidelines
GSM Association have the following policy regarding Dual (or Multi) SIM phones:
If each SIM is associated with its own transceiver, then each transceiver/SIM should have its own associated IMEI number. i.e., a dual SIM phone should have 2 IMEI numbers; a three SIM phone should have 3 IMEI numbers etc.
If each transceiver is identical, then they can share the same TAC number, but must have different IMEI numbers. If the transceivers are different (e.g. they operate on different band frequencies), then a different TAC number and a separate TAC application is required for each transceiver/SIM combination.
If you cant understand everything heres a brief description:
The structure of the IMEI is the 8 digit TAC followed by a 6 digit serial number and a check digit. These 15 digits combine to make the full 15 digit IMEI as shown below.
So as nowadays Dual SIM Phones as generally DUAL SIM active i.e. have 2 separate transceivers so they need 2 separate IMEI numbers.
In my words Each transceiver module is identified by the IMEI number (International Mobile Station Equipment Identity) for GSM transceivers.
Here is, how IMEI works :-
image source : google images.
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