HSCSD, High Speed Circuit Switched Data, is a technology which makes it possible to use several time slots simultaneously when sending or receiving data in GSM cellular networks. It has been implemented in several networks since 1999. Many networks are also upgraded to transfer 14.4 kbps per slot instead of earlier 9.6 kbps, thus HSCSD is capable of download speed 43.2 kbps (with 1 slot upstream, 3 slots downstream).