美国下面两种最新的通信交换系统,可适于各种规模铁路的通信,以提高运输效率。网络专用小交换机(PBX),它可以把相距很远的一大片铁路地区联接起来,好象在一个地区一样,不需要拨特殊的号码。专用交换机能分辩出所拨的号码,并从中取出。实际上,建立专用网,可以通过最有效的路径来处理更多的呼叫,减少公用网的使用并减少整个呼叫负荷。 The following two new types of communications exchange systems in the United States can be adapted to the communications of all sizes of railways to improve transport efficiency. Private branch exchanges (PBXs), which connect large tracts of railroads far apart, as if in a single area, without the need to dial a special number. Dedicated switches can distinguish the number dialed and removed from it. In fact, establishing a private network can handle more calls through the most efficient path, reducing the use of public networks and reducing the overall call load.