Flashing Rear End Device
Also called F…… Rear End Device or the caboose that fits in your trunk.
A FRED is a form of “End Of Train” device. The FRED sits in the coupler of the last car and connects to the air hose. It of course flashes and reads the air pressure in the train line. It can also use its sensors to determine train speed etc. The FRED transmits all of this to the conductor who now rides in the cab of the locomotive, there being no caboose.