ETSI PRTBR 15-1995 商务通信(BTC).普通质量和高质量声音带宽双线模拟租用线(A2O 和A2S)的终端设备接口附加要求
Business TeleCommunications (BTC); Ordinary and Special Quality Voice Bandwidth 2-Wire Analogue Leased Lines (A2O and A2S); Attachment Requirements for Terminal Equipment Interface