Cobra

A radar detector is an electronic device used by motorists to determine if their speed is being monitored. more...

The term originates from early speed-detection technologies, in which police bounced a radio wave off a moving vehicle with a device called a radar gun that determined the vehicle's speed by the Doppler-effect-moderated change in the wave's frequency. Most of today's radar detectors detect signals across a variety of wavelength bands - usually X, K, and Ka bands (and Ku, in Europe).

Newer speed-detection technology uses pulsed laser light (LIDAR, commonly referred to as laser detection) rather than radio waves. Modern "radar detectors" have been adapted to suit that technology, by detecting the infrared light emitted by these new detection methods. LIDAR detection is not nearly as reliable as the detection of radar, since the light is much more focused and often aimed below the windscreen level, where the detector is usually mounted. (The reflective coating of the vehicle licence plate is an excellent laser beam reflector.)

There are many products that are advertised to claim to "scramble" or "absorb" radar; many of these scrambler devices do not work at all, and if they do work, it is by emitting an active radar scrambling pulse, which makes the device illegal to operate under FCC laws.

There are a number of products that have demonstrated that they can be effective in either absorbing or jamming laser. One such product, Veil, works on the principle of absorption by reducing the light reflectivity that occurs from the preferred targeting locations on vehicles, especially the reflective vehicle registration plate; the laser used is usually infrared, so the products usually act as infrared-absorbing filters. Other countermeasures are active laser jammers from Beltronics/Escort, Blinder, and Lidatek. Since these products are regulated for eye safety by the EPA, there are currently no specific federal laws prohibiting their use, although a number of countries, states, and provinces have created laws specifically prohibiting their use to interfere with speed traffic enforcement.

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