This Recommendation describes soft error test methods for the telecommunication equipment that composes carrier telecommunications networks. The objective of soft error tests of the telecommunication equipment using an accelerator-driven neutron source is described first. The overview of the soft error tests and operating principles of an accelerator-driven neutron source are introduced next. The requirements of the accelerator-driven neutron sources and test sites are specified. The test conditions including test setup, operational conditions and error monitoring and test procedures for the telecommunication equipment are specified. Notes for determining specific, detailed test methods, such as the neutron flux to be used for irradiation and conditions for counting as failures in estimation of the reliability are also described.