GSM stands for Global System for Mobile communication. GSM PRI Gateway is a standard developed by European Telecommunication Standards Institute (ETSI) to describe protocols for second generation (2G) digital cellular networks. It was a replacement for the first generation (1G) cellular networks. The idea of developing GSM originated from a cell-based mobile radio system at the Bell Laboratories in the early 1970s. GSM is an open, digital cellular radio network operating in over 200 countries worldwide. It uses narrowband time division multiple access (TDMA) technology. It covers almost complete Western Europe and growing in America and Asia. It is not only used for voice calls, it can also be used for data computing and sending text messages. A user can connect his GSM-enabled phone with his laptop to send or receive e-mails, faxes, browse internet, check security etc GSM was developed using digital technology. It has an ability to carry 64 kbps to 120 Mbps of data rates.