A、瑞利衰落 B、擁塞 C、快衰落 D、碼間干擾
A、16kbps B、SubRTF C、FullRTF
A.1024bits/s,V.35; B.64Kbits/s,X.25; C.25Kbits/s,V.35; D.25Kbits/s,X.25.