End-of-train device
safety device mounted to rear of a train
The end of train device (ETD), sometimes referred to as an EOT, flashing rear-end device (FRED) or sense and braking unit (SBU) is an electronic device mounted on the end of freight trains in replacement of a caboose. They are divided into three categories: "dumb" units, which only provide a visible indication of the rear of the train with a flashing red taillight; "average intelligence" units with a brake pipe pressure gauge; and "smart" units, which send back data to the crew in the locomotive via radio-based telemetry. They originated in North America, and are also used elsewhere in the world, where they may include complete End of Train Air System (ETAS) or Sense and Brake Unit (SBU) devices.
Tail lamps
The earliest known method of showing the position of and completeness of a train was by the Stockton and Darlington Railway in the 1830s, where a burning brazier was attached to the rear of trains.
Under the absolute block system, each train must carry a tail lamp with a red lens on the rear. The purpose of the tail lamp is to show the signaller that the train has not separated in the previous block section, and it guarantees that the train is complete. Trains not fitted with a continuous brake were also required to carry side lamps on the rearmost vehicle; these lamps pointed forwards and showed a white light. Side lamps showed the driver of the train that their train was complete and had not separated.
End of train devices
Design and use
A "dumb" ETD can be as simple as a red flag attached to the coupler on the last car of the train, whereas "smart" devices monitor functions such as brake line pressure and accidental separation of the train using a motion sensor, functions that were previously monitored by a crew in the caboose. The ETD transmits data via a telemetry link to the Head-of-Train Device (HTD) in the locomotive, known colloquially among railroaders as a "Wilma," after cartoon character Wilma Flintstone.
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