【正确答案】 It is in emergency, also, that the station master may be called on to make decisions of considerable importance in regard to the working of the trains past his station, though in general operation control systems are now so extensively applied, more particularly to main lines, that he can obtain without any great delay a decision by telephone from the control office of the area in which his station is situated as to any altered methods of working that it may be necessary to put in force.