ES 202 971-2006
接入和终端(AT);公共交换电话网(PSTN);用于短线接口的 2 线模拟接口的物理和电气特性协调规范(V1.2.1)
Access and Terminals (AT); Public Switched Telephone Network (PSTN); Harmonized specification of physical and electrical characteristics of a 2-wire analogue interface for short line interface (V1.2.1)