电话机作为通信终端设备中的一种,它在电话用户与电信网之间构成了一个界面。电话机每次拨号或通话都不能独立进行,都必须通过电话交换机才能实现。因此,一部电话机出现不能正常拨号、振铃、通话之类的故障,并不一定都是话机本身的原因,有可能问题是出在交换机或用户环路(外线)上。这就是为什么有时电话机经反复检查没有发现毛病可就是不能正常使用的原因。我们不妨将其称之为电话机的“伪故障”。 Telephones, as one of the communication terminal devices, form an interface between the telephone user and the telecommunications network. Each dial-up or call can not be carried out independently, must be achieved through the telephone switchboard. Therefore, the failure of a telephone to dial normally, ringing, or calling may not always be the cause of the telephone itself. The problem may lie in the switch or subscriber loop (outside line). This is why sometimes the phone is repeatedly checked and found no problems that can not be used normally. We may wish to call it the “pseudo-fault ” phone.