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.

The electronic device mounted on the rear of a freight train is officially called an End-of-Train device (ETD), but it is also widely known by the acronym EOT. In North American railroad culture, it is affectionately and colloquially called a FRED (Flashing Rear-End Device). In Canada, it is specifically referred to as a Sense and Braking Unit (SBU). In 2026, these devices have almost entirely replaced the traditional caboose. Their primary function is to monitor the brake pipe pressure at the rear of the train and transmit that data via radio telemetry to the engineer in the locomotive. "Smart" ETDs can even initiate an emergency brake application from the rear if commanded by the crew. For 2026 rail safety, they also feature a high-visibility flashing red light to mark the end of the train during night operations, ensuring that signallers and other train crews can verify that the entire train consist is still connected.