be available on hand;be at sb’s beck and call; be on call at any hour stay within call
? 他答應(yīng)～，絕不延誤。He promised to be on call at any hour and would never delay for any moment.
隨叫隨到suí jiào suí dào
形容人很勤快，隨時(shí)傳喊，隨時(shí)來到。be on call at any hour, on call, be brought up to some place at any hour, at call