电话机作为通信网的终端设备和通信的基本工具,在机关单位、工矿企业等各部门及千家万户都普遍使用它。 电话机最基本的电路包括有振铃电路、拨号电路、通话电路。 现以市面上拥有量较大的HA868(Ⅲ)型按键式电话机为例,介绍电话机中最基本的电路之一——振铃电路的工作原理,及其在使用中出现故障时的检查和排除方法。 HA868(Ⅲ)型电话机振铃电路如附图、附表所示,其他型号电话机振铃电 As the basic tool of terminal equipment and communication of communication network, telephone sets are widely used by various departments and industrial and mining enterprises and other households and households. The basic circuit of telephone includes ringing circuit, dialing circuit and calling circuit. Take the HA868 (Ⅲ) type button telephone with larger market now as an example, introduce one of the most basic circuits in the telephone - the working principle of the ringing circuit and its checkup when there is a fault in use And exclusion method. HA868 (Ⅲ) -type telephone ringing circuit as shown in the attached table, other models of telephone ringing