Level crossing signals are the electronic warning devices for road vehicles at railroad level crossings. The basic signal consists of flashing red lights, a crossbuck and a bell (either a real bell or a speaker that mimics a bell sound), attached to a mast. At most crossings, the signals will activate about 30 seconds before the train arrives but there are sensors measuring speed so that the crossing knows when to activate; so, the slower the train is, the longer the delay and the faster the train is, the earlier the crossing activates. In some countries (such as the Czech Republic or Slovakia) there is also a flashing white light, which means that it is possible to pass the level crossing at a higher speed than generally allowed. At many crossings, there will be a gate added to the signal. The gates will be fully lowered 15 to 20 seconds before the train arrives. The gates will rise and the signals will shut off once the end of the train clears the island circuit. The time interval may be controlled by a level crossing predictor, an electronic device which is connected to the rails of a railroad track, and activates the crossing's warning devices (lights, bells, gates, etc.) at a consistent interval prior to the arrival of a train at a level crossing. Crossbucks also may have legends saying, for example: "RAIL ROAD CROSSING" (United States), "RAIL WAY CROSSING" (Australia and New Zealand), "PELIGRO FERROCARRIL" (Latin America, meaning DANGER RAILWAY), or be wordless (Canada and many other countries). Many states in the US are now requiring the use of this type of equipment at all newly constructed level crossings. History First devices "Wigwag" was the nickname given to a type of crossing signals once common in North America, named for the pendulum-like motion it used to signal the approach of a train. Albert Hunt, a mechanical engineer at Southern California's Pacific Electric (PE) interurban streetcar railroad, invented it in 1909 for safer railroad level crossings. He utilized alternating electromagnets pulling on an iron armature. A red steel target disc, slightly less than two feet in diameter, serving as a pendulum was attached. A red light in the center of the target illuminated, and with each swing of the target a mechanical gong sounded. The new model, combining sight, motion and sound was dubbed the "Magnetic Flagman" and produced by the