Minecraft wiki entry for Train_station, associated text: A station in the three nominally inactivated powered rails.
Two "main" boosters, made up of a detector and 2 powered rails. The detector prevents backtracking. The spacing is determined by the type of minecart.
One "station mini" booster, made up of a detector and a single powered rail. The lower amount of powered rails prevents getting stopped by a second powered rail when the speed is insufficient to go clear of it before the detector unpowers.