CALL TRANSFER METHOD IN ADDITIVE SYSTEM INTERFACED WITH EXCHANGER IN NO.7 SIGNALING SYSTEM

摘要

PURPOSE: A call transfer method in an additive system interfaced with an exchanger in No.7 signaling system is provided to reduce a system load by connecting a callee to a client only by using a call input line and cutting off a call input line when a call communication starts, since the call input line itself is in an idle state and can be used in the next service. CONSTITUTION: An exchange transmits an IAM message through the first call input line to an additive system to transfer a call(S11). The additive system transmits an ACM message to the exchanger to establish a call and completes a call connection(S12). The additive system transmits an announcement requesting of a phone number of the callee through the exchanger to a client. When the client depresses a phone number of the callee, a call transfer is requested from the exchanger through a PSTN to the additive system(S13). The additive system transmits the first user to user(USR) message to the exchanger. Upon receipt of the first USR message, the exchanger attempts a call transfer to the call through the new line on the basis of the information contained in the first USR message(S14). The exchanger checks whether the callee answers(S16). If the callee answers, the exchanger informs the additive system that the callee has answered in the second USR message(S15) and applies a release(REL) message requesting restoration of the second input line to the additive system through a pertinent call input line. The REL message includes a command for cutting off the call input line connected between the exchanger and the additive system(S17). Upon receipt of the REL message, the additive system cuts off the call input line connected to the exchanger in response to the REL message(S18) and applies a release complete(RLC) message informing that the second call input line has been completely restored to the exchanger. The call input line is connected, so that a speech path is formed between the caller and the callee and a charging is initiated(S19).