As regards economy, early studies offered significant advantages since a substantial quantity of interface equipment in the telephone exchange could be eliminated.

至于经济性，早期的研究表明，由于数字业务可以省掉电话交换中大量的接口设备，因而具有重要的优势。

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In the old economy, people travel to walk. They buy things in stores. They use the post office, the fax and the telephone to send information.

旧经济中，人们出门工作，在商店购物，用邮局、传真和电话传送信息；

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