Like the Electronic Serial Number (ESN) and later Mobile Equipment Identifier (MEID) identify CDMA-band phones, the International Mobile Station Equipment Identity (IMEI) identifies GSM-band phones. Each IMEI number is unique to the device it is attached to and not directly linked to the user of the phone. Unlike the ESN/MEID system, wherein the cellular provider associates the number with the user and their access to the cellular network, the IMEI system relies on SIM cards or other identifying components to provide the International Mobile Subscriber Identity (IMSI) number. This is why GSM-band phone users can take the SIM card out of their phone (say, in the case of malfunction) and temporarily place it in their friend’s GSM phone in order to resume making phone calls using their own phone number.
- By Jason Fitzpatrick on 07/7/13