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A radar detector is a compact electronic device utilized by quite a number of motorists in order to detect the presence of law enforcement radar units. Supposedly, a radar detector should pick up a radar gun's signal prior to the driver getting close enough to the officers to get caught. The use of a radar detector can best be noted as tolerated, and at certain states, either completely illegal, or legal. Most vehicles equipped with radar detectors, make it a point to place the unit in an inconspicuous location inside the car. What a radar detector detects is totally dependent on the model and make of the radar gun being used by traffic officers. A basic radar gun transmits a radio signal on a specific frequency. The signal gets reflected off a targeted vehicle and is returned to the radar gun. The signal the radar gun sends out moves at a constant speed, which is at the speed of light, a microprocessor calculates the time it takes for the reflected signal to return. If the vehicle is moving towards the location of the radar gun, the frequency gets compacted, or higher due to a phenomenon known as the Doppler shift. This implies that a radar gun can accurately calculate the speed of a moving vehicle. Also, law enforcers don't need to stay stationary by the side of the road to get your car's speed reading. A radar detector runs at a similar frequency as the signals emitted from radar guns, but sometimes, officers change the frequencies to keep some radar detectors off guard, as some detectors are not capable of detecting specific frequencies. In a similar sense that a radio can receive AM or FM signals, a radar detector is capable of detecting radar gun signals before the vehicle gets into enforceable distance. The detector then alerts the driver with audio and visual cues, giving him enough time to slow down within the legal speed limit. These types of detectors heavily depends on the law enforcement officers tendencies upon radar gun operation, if the officer chooses to come up quietly on a speeding car, and activates the radar gun at a very close range, the radar detector won't do much good. The latest technology in speeding detection makes use of laser beams instead of sound waves. This system is referred to as LIDAR (Light-based Detection And Ranging), and can be easily set up by traffic enforcers to automatically catch speeders, through highly accurate laser calculations. Since these laser signals are very narrowly focused, a typical radar detector, without the proper technology to defense against such signals, cannot detect LIDAR before it's too late. To compensate, detectors employ a different tactic, a signal emitted by a LED (light-emitting diode) is transmitted to effectively jam, or confuse the laser light. The LED is set to match the exact frequency of the laser beam on the gun and is mixed with additional electronic "noise", or "white noise". This causes the radar gun to produce an unintelligible reading, which happens sometimes on certain situations, which is why it cannot be used to prosecute a supposed speeder.
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