层三信令事件代码详解

1Unassiagnednumber(未分配的号码（空号）)3Noroutetodestination(无至目的地的路由)6Channelunacceptable(不可接受的信道)16Normalclearing(正常清除)17Userbusy(用户忙)18Nouserresponding(无用户响应)19Useralerting,noanswer(已有用户提醒，但无应答)21Callrejected(呼叫拒绝)22Numberchanged(号码改变)26Nonselecteduserclearing(清除未选择的用户)27Destinationoutoforder(终点故障)