所以这个数字包括已连接的主线和用于将来连接的可用主线数，包括交换技术操作主线(测试号码)。

This number includes, therefore, main lines already connected and main lines available for future connection, including those used for the technical operation of the exchange (test Numbers).

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你可能知道，房间号码的第一个数字代表楼数。

As you may know, the first figure of the room number stands for the floor.

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