Trains communicate with actuators for the points lying ahead and set signals for them. Each actuator can only set one signal (z4f), and additional arbitrary specifications (z3f). A rail section covered by a point (w3) can only be travelled across when the signal set previously by the relevant actuator allows it. The signals are usually reset by the train as soon as it has passed the point concerned. The advance of a train into the next section is dependent not only on the corresponding signals, but also on the train (z4) having communicated with the one still crossing the next section. Through a comparison of the positions of both trains, the following train maintains a safe distance from the train ahead.
