double flat meaning in English

升降记号
双经/纬（生丝疵点）
双平坦型
重降

Due to a & b double flats setting of stp ( signalling transfer point ) in different place , and working on mode of payload - sharing on signalling links ( couple links ) between sp ( signalling point ) and stp , the calling signalling sequence cannot be collected completely from single stp . thus it is difficult to synthesize signalling affair in the signalling supervision system . the first , this thesis illuminateds network architecture of no . 7 signalling network and no . 7 signalling centralized supervision system
由于七号信令网的信令转接点设备stp ( signallingtransferpoint )采用a 、 b双平面异地设置，下一级的信令点设备sp ( signallingpoint )至上一级的一对stp之间的信令路由采用负荷分担方式工作， sp至stp对的负荷分担链路形成耦合链路，导致在一个stp处无法采集到完整的呼叫信令序列，这样就给监测系统核心部分之一的信令事件合成带来了极大的难度。