1 sentence for 外线 (wài​xiàn — outside line)

1. 办公室的电话需要先拨0才能打通外线。

   bàn​gōng​shì de diàn​huà xū​yào xiān bō0 cái néng dǎ​tōng wài​xiàn.

   You need to dial 0 first to get an outside line on the office phone.

   Source: Dong Chinese Dictionary