ＥＷＳＤ程控交换机如何防止套拨天津港通信导航公司张术源，魏涛，李莹所谓套拨是用户打长途电话时拨两个区号，如图１所示。以天津、北京、乌鲁木齐三市为例，假设三市的长途局之间均有直达路由，且长途与市话局的交换机因疏忽都没有采取限制套拨的措施。图１京、津、乌... EWSD program-controlled switches how to prevent set dial Tianjin Port Communications Navigation Company Zhang, Wei Tao, Li Ying The so-called dial-up dial when the user dials two area codes long-distance calls, as shown in Figure 1. Taking the cities of Tianjin, Beijing and Urumqi as an example, it is assumed that there are direct routes between long distance bureaus of the three cities, and the switches of the long distance and the local telephone exchange have not taken the measures of arbitrating arbitrage because of negligence. Figure 1 Beijing, Tianjin, Ukraine ...