DIN EN 300450:2002
通路和終端(AT).普通質量和高質量音頻帶寬雙線模擬租用專線(A2O和A2S).設備終端接口
Access and Terminals (AT) - Ordinary and special quality voice bandwidth 2-wire analogue leased lines (A2O and A2S) - Terminal equipment interface (Endorsement of the English version EN 300450 V 1.2.1 (2001-07) as German Standard)