A.3×110×600 B.1.732×110×600 C.2×110×600
A.2850Hz和3150Hz B.2680Hz和3080Hz C.2880Hz和3080Hz
A.物理層和數(shù)據(jù)鏈路層 B.數(shù)據(jù)鏈路層和網(wǎng)絡(luò)層 C.網(wǎng)絡(luò)層和會(huì)話(huà)層