ETSI PRETS 300 002-1990 公共交换电话网(PSTN):用于PSTN上的9,600或4,800 bits/s标准化双工调制解调器认可要求(TE04-09)(候选网络25)
Public Switched Telephone Network (PSTN): Approval Requirements for 9600 or 4800 Bits per Second Duplex Modems Standardized for Use on the PSTN (TE 04-09) (Candidate NET 25)