RS4 Codici

From Wikipedia, the free encyclopedia
Jump to: navigation, search

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:

modulation frequency code meaning
(none) Assenza di Codice transmission failure, e.g. on a siding not equipped with the required track circuitry
75 / min Via Impedita the next signal is at "stop" or the train is about to enter a dead-end track, a partially occupied track or a track with particular short braking distance
120 / min Riduzione di Velocita the next signal displays a speed restriction (30 km/h, 60 km/h or 100 km/h)
180 / min Preavvisa the next signal is at "proceed", but the signal after that is at "stop" or displays a speed restriction
270 / min Via Libera proceed without restrictions

The driver must acknowledge a code change by pressing a button labeled RIC within 3 seconds, otherwise the system will apply emergency brakes.

As trains got faster and additional set of codes sent with a 178Hz carrier were added. The new system was backwards compatible with the old 4-code system as trains unable to receive the 178Hz codes would be relegated to a slower speed. The 5 additional codes are as follows.

50Hz modulation frequency 178Hz modulation frequency code meaning
120 / min 75 / min Riduzione di Velocita 100 the next signal displays a speed restriction of 100 km/h
120 / min 120 / min Riduzione di Velocita 130 the next signal displays a speed restriction of 130 km/h
180 / min 75 / min Preavvisa 150 the next signal is at "proceed", but requiring reduction in speed to 150 km/h
270 / min 75 / min Via Libera 220 proceed without restrictions at speed up to 220 km/h
270 / min 120 / min Via Libera 250 proceed without restrictions at speed up to 250 km/h

See also[edit]

References[edit]