on duty

The man on duty rang an alarm.

值员发出报。

The officers on duty were visibly overcome, many of them in tears.

那些值的官员明显不能自持，许多人都流出眼泪。

Half the garrison are on duty.

有半数卫戍部队在执勤。

The patrol police on duty are on the alert against any possible disturbances.

"值处于戒备状态,随时准备付任何可能发生的骚乱。"

In addition to these arrangements, extra ambulances will be on duty until midnight.

些安排以外，还增派救护车值到午夜。

A policeman has to keep on his toes all the time he's on duty.

察在执勤时必须时刻保持覺。

The striped band round a policeman’s sleeve is to signify that he is on duty.

察袖子上的袖标标明他正在执勤。

Eight are on duty.

八个人在值。

Six are on duty.

六个人在值。