在开发 VoIP 系统时，主要考虑的一个方面就是连接到模拟电话的接口。设计人员必须了解 PSTN 中存在的电话接口要求，因为它们必须在 VoIP 系统中得到支持。本文将重点介绍连接到标准 POTS 电话的两种最常用接口：Foreign eXchange Subscriber (FXS) 与 Foreign eXchange Office (FXO)。重点说明了设计人员在为 VoIP 小区网关的模拟电话接口提供支持时可能面临的某些挑战。-In the development of VoIP system, one aspect of the main considerations is connected to the analog telephone interface. Designers must understand the existing PSTN telephone interface requirements, because they are in the VoIP system must be supported. This article will focus on the standard POTS telephone connected to the two most commonly used interface: Foreign eXchange Subscriber (FXS) and Foreign eXchange Office (FXO). Focusing on the design staff in the Residential Gateway for VoIP analog telephone interface may provide support to some of the challenges faced.