What is a GSM phone and a SIM Card?
Conventional cell phone service providers works as follows: Each mobile phone has a unique serial number, for GSM Phones it is a “IMEI #,” which is used by the cell phone network provider to to identify who you are. It is like a unique finger print for your cell phone. The wireless service provider ‘knows’ that a particular serial number belongs to your phone and therefore knows where to send your phone calls when someone dials your phone number. A GSM phone and network service is different because it is not directly linked to your cell phone. It is linked to a chip called a subscriber information module (SIM) card that is placed in your cell phone. The SIM card behaves the same way as the serial number but it is not unique to one phone. Instead, the SIM has the unique serial number. The important difference is that you can put your SIM Card into any compatible GSM phone and that phone will now act as your phone. This is because the wireless network provider sees your SIM Card not the
