Yes, but not as well as we wish they would work! Don't depend 100% on a radar detector. There are a number of related questions and answers on WikiAnswers on radar and speed control. A link is provided.
Only if he has his radar gun on. Radar detectors are not cop detectors.
Radar detectors are legal. Radar scramblers however are NOT legal.
A cobra detector is a radar detector. Radar detectors work the same way a radio receiver does. The radar detector looks for frequencies that a radar gun uses.
The best radar detectors on the market are made by Beltronics. Beltronics is a leading manufacturer of the Vector, Professional, and Express radar and laser detectors.
Laser detectors detect laser speed devices and Radar detectors detect radar speed devices.Unfortunately it's usually too late when they detect Lasers.
Radar detectors are legal to use for all non-commercial vehicles in 49 states. Washington, DC and Virginia are the only two states that radar detectors are banned in the United States. Radar detectors used in commercial vehicles are illegal.
Radar Detectors in Oklahoma: Radar detectors are legal to use in Oklahoma.Laser Jammers in Oklahoma: Laser jammers are illegal to use in Oklahoma.Courtesy of: http://www.1stradardetectors.com/radar-detector-laws.php
Radar detectors are legal to use in Nevada, but as you stated they are illegal to sell.
Cobra radar detectors are devices used to detect if the police are monitoring your car or checking your speed limit using a radar gun. This is used by motorist so they can fix their speed before getting pulled over.
Valentine radar detectors are the most popular for their sounds.
Beltronics offers the best performing radar and laser detectors on the road, including the Professional Series models.
You can fix radar detectors for cheap by fixing them yourself. You can learn how to fix radar detectors yourself at the eHow website. Once on the page, type "How to fix radar detectors" into the search field at the top of the page and press enter to bring up the information. Alternatively, you can also learn how to repair this item at the Fixya website.