空气污染一直没有消失，但是这些专用分组交换机却已经被全被直拨电话和计算机化的路由呼叫系统替代了。
Air pollution hasn't gone away, but these PBX RIGS have been replaced just about everywhere by direct-dial phone lines and computerized call-routing systems.
许多移动电话运营公司都使用两档计费系统，分别对呼叫的每一档进行单独计费。
Many cell phone companies use a two-leg billing system that bills each leg of the call separately.
清扫人员从房间中呼叫电话系统。
The cleaning personnel calls the phone system from the room.
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