My extension is two four double 0.

　　我的分機號是2400。

　　The extension of the subway will take several months.

　　擴建地鐵需用幾個月時間。

　　He's been granted an extension of the contract for another year.

　　他的合同獲得延期一年。

　　You can reach me at 637-2335, extension 354.

　　你可以打637-2335這個電話號碼，轉分機354，與我聯系。

　　What's your extension number?

　　你的分機號碼是多少？