High Speed Circuit Switched Data (HSCSD) is an evolution of Circuit Switched Data (CSD). It is the initial mechanism for data transmission in the Global System for Mobile communications (GSM) standard. HSCSD has data transmission rates as fast as 38.4 kbits/s.

The HSCSD enhancement uses multiple channels, thus enabling higher transmission rates. This allows users to benefit from faster e-mail, Internet, and file transfer service. HSCSD also offers access to non-voice services at approximately three times the speed of the earlier systems. Users can receive and send data using personal computers at speeds as fast as 28.8 Kbps. In certain networks, speeds can reach as fast as 43.2 Kbps.

Subscribers may use this system through HSCSD-compatible voice terminals or a portable computer card and a GSM mobile phone. This combination renders laptop computers and other portable devices into high-speed mobile offices. These offices give the user hands-free voice calls and convenient data transfer functions.

HSCSD is valuable to users who access their e-mail, the Internet, office intranet, or other access files. Even if a user is out of the office or travels to another country (where HSCSD roaming is accessible), connection to a home Internet Service Provider (ISP) or to an office is possible. Here, data transmission uses the cellular or mobile device as opposed to a fixed connection line, thus giving the user benefits in terms of major improvement in data transfer rate.

HSCSD is now accessible to approximately 90 million subscribers in 25 countries across the globe. This enhancement will soon be available in HSCSD-enabled GSM mobile handsets (as well as PC-compatible devices) through International Roaming arrangements among HSCSD service providers worldwide.