This standard specifies the lightning protection technical requirements and test methods for telecommunications terminal equipment (hereinafter referred to as TTE). This standard is applicable to telecommunications terminal equipment such as telephones, fax machines, modems, and multimedia user terminals where metal wires are directly connected to balanced pairs. It serves as the technical basis for lightning protection design and lightning overvoltage testing of such equipment. This standard does not include tests for direct lightning strikes. 2. The provisions contained in the following standards constitute the provisions of this standard by reference in this standard. At the time of publication of this standard, all versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB 3482-83 Electrical Equipment Lightning Test Methods GB 3483-83 Guidelines for Lightning Test of Electronic Equipment GB 4913-1995 Safety of Information Technology Equipment (including Electrical Affairs Equipment) Definition 3.1 "Non exposed" Environment In urban centers and areas with low thunderstorm activity, the overvoltage rarely exceeds the residual overvoltage of protective devices, This environment is called a "non exposed" environment. 3.2 "Exposed" environment Other than the "non exposed" environment, including some abnormal environments where satisfactory business quality can only be achieved by taking all practical protective measures