家里或办公室里为了通话方便常在一对电话线上装有两台同线电话,遇有来话打入时用任一台电话机均可接听。这种同线电话的缺点一是在接听电话时另一台电话机可以监听,因此不保密;二是两台话机同时处于摘机状态时,通话音量变 In the office or in the office in order to facilitate the call often in a pair of phone lines with two same-line telephone, in case of incoming call with any telephone can answer. The disadvantage of this type of same-line telephone is that one of the other telephone sets can intercept while answering the call, so it is not kept secret. Second, when the two telephone sets are both in the off-hook state, the call volume is changed