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<h3>Some features to look for:</h3> <dl> <dt>Type of detector:</dt> <dd>There are three types of radar detector: corded, cordless, and remote-mount. <span class="define">Corded detectors</span> usually mount on the windshield via suction cups, and provide the best range of detection. <span class="define">Cordless detectors</span> are transported easily between vehicles, and provide a cleaner installation than corded models. <span class="define">Remote-mount detectors</span> are permanently mounted to your vehicle, providing a clean installation that's virtually undetectable by thieves.</dd> <dt>City Modes:</dt> <dd>City mode turns down the range or sensitivity so that you get fewer false alerts; this feature is helpful for urban driving.</dd> <dt>Laser detection:</dt> <dd>A detector with one laser sensor can detect laser beams in front of you, but not behind you or off to the sides. 360-degree laser detection uses two sensors to look for laser pulses to the sides and behind you. Models with 360-degree laser detection tend to be more reliable, but more costly.</dd> <dt>VG-2 and Spectre protection:</dt> <dd>These are shielding technologies that let you know when police are using radar detector detectors (RDD). Spectre is a more advanced RDD technology that is currently being used in several states and Canada. Some detectors offer <span class="define">Stealth</span> protection, which warns you and then shuts down the detector, while more expensive detectors offer <span class="define">Invisible</span> protection — they may be shielded from VG-2, Spectre, or both, so they can continue operating without being discovered.</dd> <dt>Digital voice alerts:</dt> <dd>A voice alert tells you what your radar detector has picked up. You don't have to take your eyes off of the road to look at the detector's display.</dd> <dt>"Instant-On" Protection:</dt> <dd>Practically speaking, you can't really defend yourself against Instant-On radar; if it's been aimed at you, your speed has been measured by the time your detector gives an alert. However, if the radar was targeted on a car ahead of you, a detector with sensitive K-band reception will alert you. High K-band sensitivity is what allows manufacturers to promote a detector as giving Instant-On Protection.</dd> </dl> <h3>Radar Detectors: Treat yourself to peace of mind</h3> <p>The freedom to relax and drive with confidence that's what an investment in a radar detector can give you. Today's models combine simple, ergonomic design with up-to-the-minute technology. They can offer you affordable, convenient protection, not only from speeding tickets but often from driving hazards, as well.</p> <h3>How radar detectors work</h3> <p>Think of a radar signal as a beam of light from a flashlight. When you shine a flashlight at an object, your eyes perceive the light reflected from the object. Now imagine yourself as the object being illuminated. You can see the light from the flashlight from a much farther distance than the person with the flashlight could ever hope to see you. That's because the beam loses energy over distance. So while the beam has enough energy to reach you, the reflected light doesn't have enough energy to travel all the way back to where it started.</p> <p>Police radar guns "see" a vehicle by transmitting a microwave pulse. Then they make use of the Doppler Effect: the frequency of the transmitted pulse is compared to the frequency of the reflection, and speed is calculated by using the difference between them.</p> <div class="image-center"> <img src="http://akamaipix.crutchfield.com/ca/learningcenter/car/radar1.gif" width="316" height="151" alt="Radar diagram" /> <span class="caption">Speed is calculated when a pulse is reflected to the RADAR transmitter.</span> </div> <p>That's the idea behind radar detectors. They look for radar "beams" and find them before they can return a strong enough reflection to "illuminate" you. Detectors use something called <a href="/learningcenter/car/radar_glossary.html#superheterodyne">superheterodyne reception</a> to accomplish this. Radar detectors are essentially microwave radio receivers that make noise or flash lights when they sense an incoming signal on specific frequencies. Superheterodyne reception allows detection of radar around curves or over hills, and it extends detection range straight ahead.</p>
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