本指南包含在电力系统继电保护的电话通道上应用音频通信的信息和建议。它旨在涵盖租赁和私人电话系统的应用，但不包括私人微波或载波信道的应用。包括发送和接收设备、租用的电话通道、应用原理、安装和测试部分。这项工作反映了设备制造商和电话公司以及用户的知识和经验。还包括之前发布的相关信息

This Guide contains information and recommendations for applying audio-tone communication over telephone channels for power-system relaying. It is intended to cover applications to both leased and private telephone systems but not applications to private microwave or carrier channels. Included are sections on transmitting and receiving equipment, leased telephone channels, application principles, installation, and testing. Reflected in this work is the knowledge and experience of equipment manufacturers and telephone companies as well as that of the users. Pertinent information previously published is also included