【计】 忙碌信号, 占线信号

若要接听或打出重要电话，可先暂时取消「来电待接」讯号，如再有第三者打入电话，对方会听到线路繁忙讯号，而用户也不会听到「来电待接」讯号。

be busy doing

busy

as busy as a bee

get busy

much too busy

busy hour

engaged line【通信】;busy line【通信】

device busy【计】