Business TeleCommunications (BTC); 64 kbit/s digital unrestricted leased line with octet integrity (D64U); network interface presentation; English version ETS 300288:1994
Access and Terminals (AT) - Multiple 64 kbit/s digital unrestricted leased lines with octet integrity presented at a structured 2 048 kbit/s interface at either or both ends (D64M) - Connection characteristics and network interface presentation
