Now they all use column tails (as shown in the picture)

Before 1980' s in China, the carriage was a kind of carriage hanging at the tail of a freight car. Its function is to monitor the operation of freight cars, especially whether the brake air pressure in the air duct at the rear of the train is normal, and report it to the driver at the head of the train. In the 1990s, the caboose on the trunk railway was completely cancelled and replaced by an electronic device called "train tail device", which was hung on the last carriage and automatically sent the wind pressure data of the brake duct at the rear of the train, which was received by the wireless receiving device in the locomotive.