on duty

The man on duty rang an alarm.

值班员发出警报。

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

"值班巡警处于戒备状,准备应付任何可发生的骚乱。"

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

警察袖子上的袖标标明他正在执勤。

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

除了这些安排外，还增派救护车值班到午夜。

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

警察在执勤必须刻保持警覺。

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

那些值班的官员明自持，许多人都流出了眼泪。

Eight are on duty.

八个人在值班。

Six are on duty.

六个人在值班。

Half the garrison are on duty.

有半数卫戍部队在执勤。