The AMR (Adaptive Multi-Rate) standard is a speech coding algorithm that operates at variable bit rates in the range of 4.75 to 12.2 Kbps in its narrowband configuration. This technology was initially developed for the GSM system, the single most deployed 2G mobile telecommunication system worldwide, used mostly in Europe and Asia. It was later adapted by the 3GPP as the mandatory codec for 3G wireless systems based on the evolved GSM core network (WCDMA, EDGE, GPRS). The AMR narrowband codec was standardized by the European Telecommunications Standards Institute (ETSI) in 1999.