A.外線絕緣不良B.外線斷線C.外線混線D.數(shù)據(jù)信號(hào)未到達(dá)
A.線路混線B.線路斷線C.話機(jī)障礙D.線路干擾
A.環(huán)路B.切斷C.復(fù)接D.剪斷