市面上销售的电话机很多不带电路原理图，有的虽然附有电路图，但由于用户保管不善而遗失。因此，当话机出现故障时，维修人员难以尽快排除。 怎样在缺少电路图的情况下有效地检修各种电话机呢？笔者通过初步总结，向大家介绍下面三种最基本的方法： 一、故障分类法 一般电子电 Many phones on the market do not sell circuit schematics, although some with circuit diagrams, but due to poor user custody and lost. Therefore, when the phone fails, maintenance staff hard to rule out as soon as possible. How to effectively repair all kinds of telephones in the absence of circuit diagram? The author through the initial summary, to introduce the following three kinds of the most basic method: First, the fault classification method General Electronic