History
GSM stands for Global System for Mobile Communications and is one of two major global technologies developed for digital cellular networks. The other major such standard is CDMA (Code Division Multiple Access). GSM phones are recognized by the presence of a SIM or Subscriber Identification Module, which contains the user's subscriber information. GSM is a cellular network, which means that mobile phones connect to the network by searching for cell towers in the immediate vicinity. These cell towers broadcast the GSM signal. GSM communicates across radio spectrum bands (think of them as