ISO/IEC 23915:2005规定了“QSIG”和会话启动协议（SIP）之间的信令互通，以支持企业电信网络（CN，也称为企业网络）内的呼叫转移。 “QSIG”是一种信令协议，在专用综合业务网（PISN）内的专用综合业务网交换机（PINX）之间运行。PISN为用户提供电路交换的基本业务和补充业务。 SIP是用于建立、终止和修改多媒体会话的应用层协议。它通常通过IP进行传输。 ISO/IEC 23915:2005规定了在采用QSIG的PISN和采用SIP的企业IP网络之间建立呼叫期间，呼叫转移的信令互通。 它既包括QSIG网络中呼叫转移对SIP的影响，也包括SIP网络中请求重定目标对QSIG的影响。 ISO/IEC 23915:2005适用于任何可以充当采用QSIG的PISN和采用SIP的企业IP网络之间网关的互通单元。

ISO/IEC 23915:2005 specifies signalling interworking between "QSIG" and the Session Initiation Protocol (SIP) in support of call diversion within corporate telecommunication networks (CN), also known as enterprise networks. "QSIG" is a signalling protocol that operates between Private Integrated services Network eXchanges (PINX) within a Private Integrated Services Network (PISN). A PISN provides circuit-switched basic services and supplementary services to its users. SIP is an application layer protocol for establishing, terminating and modifying multimedia sessions. It is typically carried over IP. ISO/IEC 23915:2005 specifies signalling interworking for call diversion during the establishment of calls between a PISN employing QSIG and a corporate IP network employing SIP. It covers both the impact on SIP of call diversion in the QSIG network and the impact on QSIG of request retargeting in the SIP network. ISO/IEC 23915:2005 is applicable to any interworking unit that can act as a gateway between a PISN employing QSIG and a corporate IP network employing SIP.