To convey the tone information,the local MG issues a notify event,which tells the MGC about the fax tone detection.The MGC then issues a command to the remote MG requesting that it replay the fax tone.

• 为传达这个呼叫音，本地的MG发一个通告事件，告诉MGC检测到了传真呼叫音，然后MGC发一个命令给远地的MG，请求它重新发出传真呼叫音。