The Global Positioning System is a "constellation" of 24 satellites that orbit the Earth at a height of 10,900 miles, making it possible for people using ground receivers to determine their geographic location within 10 to 100 meters. The satellites use simple mathematical calculations to broadcast information that is translated as longitude, latitude and altitude by Earth-based receivers.

GPRS

General Packet Radio Service technology runs at speeds up to 115Kbit/sec., compared with the 9.6Kbit/sec. of older GSM systems. It enables high-speed wireless Internet and other communications such as e-mail, games and applications. It supports a wide range of bandwidths and is an efficient use of limited bandwidth. It's particularly suited for sending and receiving small amounts of data, such as e-mail and Web browsing, as well as large volumes of data.

GSM

Global System for Mobile Communications is a digital cellular system based on TDMA narrowband technology, which gives users access to time slots on the same frequency bands. It allows up to eight simultaneous communications on the same frequency. It competes with CDMA.