Global System for Mobile Communications (GSM)

Digital cellular communications standard developed in Europe and now used in more than 160 countries. It employs narrowband time division multiple access (TDMA) technology which allows eight simultaneous calls on the same 200 kilohertz (kHz) wide communication band at speeds up to 9.6 kilobits per second (kb/s). Commercially introduced in 1991 and continually updated, GSM provides a high degree of security by using subscriber identity module (SIM) cards and an advanced encryption scheme. In addition, it offers a bi-directional short message service (SMS) for up to 160 bytes (about 160 characters) long alphanumeric messages which can also be used for broadcasting news clips. GSM is available in three frequencies: 900 Megahertz (MHz) used in most of Europe and some 100 countries around the world; 1800 MHz used mainly in some countries of Europe, Southeast Asia and Pacific Rim, and Australia; and 1900 MHz used mainly in the US, Canada, and parts of Latin America and Africa. Also called Global System For Mobiles. See also General Packet Radio Service (GPRS).