What is GSM

GSM (Global system for Mobile communications) is the international standard  for mobile telephony through out the world.  In covered areas, mobile phone users can buy one phone that will work anywhere where the standard is supported. To connect to the specific service provider in a particular place, GSM users simply switch the Subscriber Identification Module (SIM) cards. SIM Cards are small removable disks that slip in and out of GSM cell phones. They store all the connection data and identification numbers you need to access a particular wireless service provider.

It is estimated that more than 80% of the mobile phone users in the world use GSM.   GSM is considered as the second generation technology in mobile phones.  The GSM networks operate in different frequency bands of operation.  Most of the GSM networks in the world operate at 900 MHz frequency or the 1800 MHz band.   In some places the 850 MHz and 1900 MHz bands are also used.  Very rarely 400 and 450 MHz bands are also used in some places.  The transmitted power of GSM phones is limited to around 2 Watts.