Those who did try to return calls found the lines busy (just in case people think I mean deliberately jammed), leading to critical communication lags amid a constantly shifting situation.

有些人想打电话回去的，但线路总是忙音(这让人认为是故意把线给卡了)，形势瞬息万变的时刻，通信偏偏拖慢了后腿。

youdao

Ingrid was busy learning her lines for the next day's shooting.

英格里德正忙着背第二天拍摄的台词。

《柯林斯英汉双解大词典》

This is a nice way to start the day and a good way to ensure open lines of communication in a very busy household.

在一个忙忙碌碌的家庭中这是一天中好的开头同时也能保证大家从开始就能互相交流。

youdao

Orders for commercial airplanes are expected to be lower this year, as airlines cope with an expected America's Boeing executives in Dubai put on a brave face, saying that fulfilling back orders will keep their production lines busy.

VOA: standard.2009.11.15

In North America the assembly lines are busy, but cheap imports push down prices.

ECONOMIST: Mercedes goes to Motown

If the lines are busy, an answerphone message tells children to keep redialling.

BBC: NI Childline 'in need of funds'

And while some are busy commuter lines, others are off-the-beaten-track gems that are well-worth connecting to.

BBC: Majestic Canada, coast to coast