Completion of Calls on No Reply (CCNR) is an ISDN supplementary service offered to the calling user.
无应答时呼叫的完成(CCNR)是一种向主叫用户提供的ISDN补充业务。
2
The ECT supplementary service enables an ISDN user who has two calls, into one call.
ECT补充业务能使具有两个呼叫的用户转移到一个呼叫中去。
3
These procedures may be used for the invocation and operation of supplementary services in association with existing calls or outside any existing calls.