The International Telecommunication Union (ITU) has worked out technical specifications for ADSL full rate - with speeds up to 8 Mbit/s downstream and 1 Mbit/s upstream - in its Recommendation G.992.1. This includes a number of country-specific variants in order to accommodate regional local loop infrastructure differences. ADSL can achieve its highest speeds at a distance of 4 km or less. The connection also allows the provision of voice phone service on the basic frequency band of the same line.
