DIN EN 300012-1-2001 综合业务数字网(ISDN).基础用户网络接口(UNI).第1部分:层1规范
Integrated Services Digital Network (ISDN) - Basic User Network Interface (UNI) - Part 1: Layer 1 specification (Endorsement of the English version EN 300012-1 V 1.2.2. (2000-05) as German standard)