RS4 Codici
From Wikipedia, the free encyclopedia
RS4 Codici is a train protection system used in Italy. The term is an abbreviation of Ripetizione Segnali a 4 codici (signal repetition system with 4 codes).
It is a simple cab signalling system, displaying the aspect of the next (and, in some cases, the next but one) signal. It helps the driver to reliably determine the aspect of the next signal even in poor visibility and at high velocities.
The information is conveyed via amplitude modulation of a 50Hz alternating current in the rails. Receiver coils in front of the first axle of a locomotive or control car are used to detect the signal.
The frequency of the modulating signal encodes the signal aspect:
- 75/min - "Stop"
- 120/min - "Proceed slow" (30km/h, 60km/h or 100km/h)
- 180/min - "Caution, next signal at stop or slow" (i.e. the signal the train is approaching is at "Caution" and the next signal after that is at "Stop" or "Proceed slow")
- 270/min - "Proceed with line speed"
The driver must acknowledge a code change by pressing a button labeled RIC within 3 seconds, otherwise the system will apply emergency brakes.
