Minecraft wiki entry for Detector_Rail, associated text: powers adjacent redstone dust and adjacent redstone repeaters facing away from the detector rail, to power level 15
powers adjacent redstone comparators facing away from the detector rail to a level corresponding to the fullness of the minecart if it is a Minecart with Chest or a Minecart with Hopper.
strongly powers any full solid opaque block beneath the detector rail to power level 15
activates any adjacent mechanism components, including above or below, such as pistons, redstone lamps, powered rails, hoppers, etc.