本文件的目的是记录555 NXX线号的历史，包括1994年创建555 NXX分配指南之前的使用情况，以及2016年指南日落之前的使用情况。本文件还涉及与实施相关的问题、任务数据摘要、行业编号委员会（INC）2016年关于555 NXX任务指南的协议，以及如果INC确定并同意对资源的需求，将确定555行号的未来的协议。

The purpose of this document is to capture the history of the 555 NXX line numbers, including the uses prior to the creation of the 555 NXX Assignment Guidelines in 1994, to the sunset of the Guidelines in 2016. This document also addresses issues associated with implementation, a summary of assignment data, the Industry Numbering Committee's (INC) 2016 agreement to sunset the 555 NXX Assignment Guidelines, and agreement that the future of 555 line numbers will be determined if a need for the resource is identified and agreed to by INC.