Category: Operations/Technology
Statement: Frequent intervals, the foundation of S-Bahn operations Accompanying items: Signal box technology, train group signs, operational documents, signal models
A high-capacity, safe, and frequent train service is only possible with a purpose-built signal system. The electrification of Berlin's urban, city-ring, and suburban railways in the 1920s brought significant changes in this area. On the heavily trafficked inner-city sections, the old, manually operated semaphore signals were no longer sufficient. An automated track block system was introduced, controlled by the trains, allowing for closer signal intervals.
The electrically operated daylight signals connect the main signal to the announcement of the next signal (the distant signal). A frequency of up to 90 seconds between trains became possible. These signals ("Sv signals") were adapted technically according to their specific location within the network and came in two forms: the 'city line' type with fixed individual panels, and the modern 'ring line' type with interchangeable panels.
When a signal displays a stop, a triggering lever on the train, if it passes the signal, activates the track release and triggers an automatic brake. Modern "Ks signals" and electromagnetic safeguards ("balise") have since replaced the older types, but the fundamental safety system remains the same and continues to be reliable.