A crocodile is a component of

train protection system A train protection system is a railway technical installation to ensure safe operation in the event of human error. Development Train stops The earliest systems were train stops, as still used by the New York City Subway, the Toronto subway, t ...

s used in

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

and

Belgium Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to th ...

. It works similarly to the

Automatic Warning System The Automatic Warning System (AWS) was introduced in the 1950s in the United Kingdom to provide a train driver with an audible warning and visual reminder that they were approaching a distant signal at caution. Its operation was later extended t ...

(AWS) used in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...

. Communication between the ground-based signalling system and the in-cab equipment is made by the crocodile, an electrical contact placed between the rails and a metallic brush mounted beneath the locomotive cab. It is distinctively French, originating on the Chemins de Fer du Nord around 1872, spreading throughout France and penetrating into Belgium and Luxembourg after 1900. It was intended principally to provide evidence of the alertness of the driver, not to act to control a train automatically. The crocodile is an invention of the engineers Lartigue and Forest. Originally it was placed 100–200 metres in front of a distant signal, usually a red disc of "deferred stop". When recording of cab signals was introduced, the device was moved closer to the signal, most often directly opposite it, to reduce the chance of a change of the signal between the time the locomotive passed over the crocodile and when the locomotive actually passed the signal. If a signal changed suddenly to a caution or danger

aspect Aspect or Aspects may refer to: Entertainment * ''Aspect magazine'', a biannual DVD magazine showcasing new media art * Aspect Co., a Japanese video game company * Aspects (band), a hip hop group from Bristol, England * ''Aspects'' (Benny Carter ...

in the face of the driver, it would appear that he had not noticed it and had been surprised, when that was not the case. The crocodile can provide two different pieces of information to the driver, according to the aspect of the corresponding signal: * The "''Répétition Signal Fermé''" (which literally means "repetition of closed signal"), corresponding to a caution or danger signal, applies a +20 V voltage to the crocodile, causing a warning horn to beep in the driver's cab. Then, unless the driver pushes the acknowledgement button within five seconds, the emergency brakes are applied automatically. * The "''Répétition Signal Ouvert''" (which literally means "repetition of opened signal"), corresponding to a proceed signal, applies a -20 V voltage to the crocodile, causing a bell to ring in the driver's cab.

References

{{Railway signalling Train protection systems