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Radar detectors glossary

Key terms for understanding radar detectors

Radar detector in windshield

Radar detectors can help ease your mind as you drive, but all the technology involved might leave you scratching your head. Here’s a list of common terms associated with radar/laser detectors and radar detector detection (RDD) devices.

Shop all radar detectors

Click on a letter below to jump to that section of the glossary.



Audio/Visual Alerts

The most common audio warning is a series of "beeps" or "braps" that grow faster as you near the radar source. Visible alarms can be either a digital display of signal strength or a series of LEDs. Many detectors now offer alphanumeric LEDs which can show you the type of band detected along with its strength.


Replaces a continuous audio alert with a single alert followed by clicking. This can preserve your sanity during extended radar encounters while continuing to notify you of the presence of radar.

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City/Highway Switch (City/Highway Modes)

Helps eliminate false alarms from non-police X-band emissions encountered in urban areas, typically caused by automatic door openers at stores near the road. This is usually accomplished by reducing the detector's sensitivity since the ability to "see" long distances is not critical on city streets. Some detectors feature multiple sensitivity settings for city driving.

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Dash Mount

Velcro strips usually serve to keep the detector in place.

Dim/Dark Mode

For keeping the detector inconspicuous while driving at night, this feature dims or eliminates illumination on alarms and controls.

[Radar detectors that feature dark mode]

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False Alert or "Falsing"

Sometimes your radar detector gets set off by things that aren’t radar or laser enforcement devices. These “false alerts” are usually caused by automatic door openers, roadside traffic monitors and electronic warning signs, emergency vehicles, and in-vehicle technologies (IVT). These sources use signals which operate on wavelengths similar to that of police radar. Adjusting the radar detector’s selectivity and sensitivity levels can help filter some of these sources out, but going too far may cause the detector to miss actual police radar. False alerts are annoying and too many false alerts can cause a driver to either turn off the detector or ignore actual threats.

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Radar detectors with GPS technology don't provide turn-by-turn navigation. Instead, they use GPS satellites to keep track of vehicle speed and provide warnings for when it exceeds a user-defined limit. They also allow the user to mark locations where there are known radar enforcement areas ("speed traps"), or where there are often false alerts, so the detector can either send a warning ahead of approaching those areas, or ignore the false alerts upon return visits.

Some detectors with GPS can also access a database of traffic and red-light cameras, so the detector can provide warnings when those cameras are imminent.

GPS can alert you to red light cameras and speed traps

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"Instant-On" Protection

K-band radar guns have what's known as "Instant-On" radar. This keeps the transmitter in "hot standby" mode, ready to be activated by an officer when the target is within 200-300 yards. 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.

In-vehicle Technology (IVT)

Modern vehicle safety features can reduce certain types of accidents but also increase the likelihood of radar detector falsing. In-vehicle technologies include adaptive cruise control, forward collision avoidance, and lane departure warnings. Each of these uses in-vehicle transmitters and proximity sensors to track the vehicle’s speed and direction, and they can trigger nearby radar detectors.

In-vehicle technology uses radar and other sensors that may trigger radar detectors

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The most frequently used radar frequency band: 24.05 - 24.25 GHz. K-band made its appearance in 1978. The first K-band hand-held radar guns could only be used from a stationary position. Later, a "pulsed" version was introduced that could be used from a stationary or moving vehicle.

K-band radar waves have a relatively small wavelength. At the power level found in police radar guns, K-band has an effective clocking range of about 1/4 mile. Depending upon terrain (around a corner, over a hill, etc.), K-band waves can be detected from a range of 1/4 mile to 2 miles.


In 1987 the FCC allocated a frequency on yet another band, Ka, for police radar use. Ka-Band incorporates Ka-Band, Ka Wide-Band, and Ka Super Wide-Band. With Ka came the introduction of photo radar (also known as "photo-cop"). The photo-cop system works at 34.3 GHz and combines a Ka-band radar gun with an automated camera (see Photo Radar below).

The FCC later expanded Ka-band radar use to a range of 34.2 to 35.2 GHz. This became known as Ka Wide-Band.

The introduction of the "stalker" radar gun raised the stakes in the detection game. Unlike all previous guns, the Stalker can be FCC licensed for any frequency in the Ka-band between 33.4 GHz to 36.0 GHz, and so cannot be picked up by detectors designed only for X, K, and photo radar. Stalker guns are being used in more than half the country.

In response, manufacturers have developed detectors with "Super wide-band" technology that sweeps all of the Ka-band allocated to radar, as well as providing continued protection against X, K, and photo radar.


Ku-band radar ranges between 12 and 18 GHz. It is used primarily for satellite communications, in both aerospace and broadcasting. It is used primarily in Europe and not seen much in America. In the radar enforcement realm, Ku is set at 13.45 GHz by the FCC and has only recently been introduced to the U.S. for speed detection.

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Police laser uses laser light pulses rather than radar radio waves found in police radar detectors for speed detection. The laser speed gun has found its way into the hands of state and local police in at least half the country. LIDAR (or lidar) is often used in place of “laser” when referring to traffic enforcement. It stands for light detection and ranging or light imaging, detection, and ranging.

The advantages of a laser gun are compelling: the laser light beam is far narrower than a radar beam, allowing more accurate pinpointing of a specific vehicle; and the time needed for capturing a speed reading is less than half a second versus 2 to 3 seconds for radar.

The drawbacks are also important to note: laser guns are very expensive, they can't be used from a moving vehicle or from behind glass, and accurate aiming requires a tripod or a very steady hand.

Despite initial claims that the energy from a laser gun is not detectable, it is. And as the laser beam moves away from the laser gun, it widens and becomes easier to detect. Vehicle speeds are typically measured at roughly 1,000 feet (1/5 mile); at that distance the laser beam is over 3 feet wide.

Police officer with laser gun

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Mute or Volume Control

Allows you turn down or turn off a detector's audible alerts, while keeping the visual alerts.

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Photo Radar (Photo Cop)

The photo-cop combines a Ka-band radar gun with an automated camera. A vehicle approaching at or above a predetermined speed will trigger the camera. The photo shows the front of the vehicle, license plate, driver's face, the date, location, and time. The unit can clock and photograph up to 200 vehicles per hour. Alleged speeders are not stopped. The film is processed and a ticket is mailed to the registered owner of the vehicle, ordering him or her to pay the fine or appear in court.

Photo cop's effective range is 120-300 feet and it transmits a continuous signal, which is a plus for radar detectors. The distance at which it can be detected varies depending upon a detector's Ka-band sensitivity. Better detectors can typically sniff out a photo-cop system 1/4 to 1/2 mile away.

Only a handful of cities use photo radar. Industry sources predicted widespread interest and expanded use, but that has not been the case. Legal controversies along with prohibitive expense have caused officials to stick with more traditional methods of speed detection.

Speed camera sign

Pulse Radar

A refinement of the original K-band radar gun. Pulse radar can be used from a moving vehicle as well as from a stationary position. Pulse radar guns transmit a burst of energy every two seconds.

[Radar detectors with pulse warning]

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Radar Detector Detection (RDD)

You can think of radar detector detection as law enforcement striking back against radar detectors. VG-2 technology identifies vehicles with operating radar detectors by seeking out emitted frequencies from the tuning oscillators of radar detectors. Fortunately, most detectors provide some form of protection against this technology. Detectors with VG-2 immunity are shielded from VG-2 police radar detectors without interrupting radar and laser protection. Other detectors simply emit a warning and shut down automatically when they sniff out VG-2 signals.

Spectre RDD sweeps a larger spectrum than VG-2 and also covers multiple bands, making it more difficult to elude. It is used primarily in areas where radar detectors are illegal, or to track detectors in commercial vehicles. Only a handful of detectors today claim to be completely invisible to both Spectre and VG-2 RDD cop radar.

[Radar detectors with VG-2 detection]

Remote Mount

A two-piece detector system in which an antenna is mounted behind your car's front grille, while the control and display are installed in or under the dash. The two pieces are connected by a cable or wireless transceiver. With a remote-mount you sacrifice a small degree of sensitivity (the higher a detector is mounted, the better) in exchange for low visibility.

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Safety Warning System (SWS)

SWS uses radar to promote highway safety by transmitting a signal to alert you of changing or potentially hazardous road conditions such as highway construction sites, accidents and railroad crossings. Most radar detectors detect SWS signals and include a separate alert signal to distinguish them from radar being used for speed detection.


A detector's ability to detect police radar while ignoring the presence of such devices as automatic garage door openers and microwaves, which may operate on closely neighboring frequencies. A good radar detector offers high selectivity as well as being highly sensitive.


A detector's ability to detect radar. Most radar detector manufacturers increase sensitivity as they add features and move up the product line.


A special type of 12-volt power cable that features built-in controls and indicators for the radar detector. A mute button, alert light, and power indicator are three typical elements found on most SmartCords.

Spectre detection

A newer form of radar detector detection (RDD). See Radar Detector Detection.

"Stalker" Radar Gun

A hand-held, stationary radar gun that can be set to operate anywhere on the Ka-band between 33.4 and 36.0 GHz. Radar detectors must be able to scan a range of frequencies to detect it. These are referred to as Super Wide-Band Detectors — the latest generation of radar detectors specifically designed to pick up X, K, and the full range of Ka-band frequencies.


The term superheterodyne refers to a method of designing and building wireless communications or broadcast equipment, particularly radio receivers in which a locally generated frequency is combined with the carrier frequency to produce a supersonic signal that is demodulated and amplified. Sometimes a receiver employing this technology is called a "superheterodyne" or "superhet."

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Text Display

A text display spells out what form of speed detection you're up against. Most units with a text display also specify the type of SWS alert.

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VG-2 detection

An older form of radar detector detection (RDD). See Radar Detector Detection.

Visor Mount

Visor clips attach the detector to the sun visor.

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Windshield Mount

Suction cups and a bracket attach the detector to the windshield.

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The first frequency band allocated for police radar: 10.5 - 10.55 GHz. Dating from the 1950s, X-band radar is the easiest to detect because of its lower frequency and higher power output. Depending on terrain, temperature and humidity, X-band radar can be detected from a distance of 2 to 4 miles, yet it can only take accurate readings of speed from a distance of 1/2 mile or less.

Unfortunately, police radar is not the only source of X-band signals. Garage door openers, microwave intrusion alarms, microwave towers, and other high-tech equipment can fool a radar detector into giving off an X-band alert. Filters and redundant sampling are used to combat this "falsing."

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We hope this helps answer some of your questions about radar detectors. You might also want to read our Radar Detector Buying Guide. And if you do have any more questions or want some help in choosing a radar detector, contact one of our advisors.

  • Christopher Washington from Charlotte N C

    Posted on 4/15/2021

    Let me know what ban should I use on the highway

    Commenter image

    Dominic DeVito from Crutchfield

    on 4/16/2021

    Hi Christopher - you'll probably get the best results by using the K or Ka band on your radar detector. Many detectors have a "Highway" mode, so consult your owner's manual for details.
  • Mahlea from Olympia

    Posted on 12/20/2019

    I am wondering if you can help me with a A couple questions. First things first what would cause my radar detector to start beeping like crazy when pulling into the parking lot of a grocery store or a big chain type store....for example I was pulling into a grocery store or a major chain store like Fred Meyer.

    Commenter image

    Dominic DeVito from Crutchfield

    on 12/20/2019

    Hi Mahela - Some automatic door opener systems use microwaves that operate in the same frequency as the K-band found in common radar guns. This is what is causing your detector to sound an alert near large stores. If your detector has a K-band filter you should enable it to see if that takes care of the problem. If the detector can alternate between "city" and "highway" sensitivity modes, putting it into "city" mode might also help (it should render the detector less sensitive but it will also give you fewer false alerts for signals that are not actually from radar guns). If you bought your detector from Crutchfield, one of our Tech Support crew should be able to help you further should you need it - just give them a call.
  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 10/2/2017

    Thanks for your suggestions, Ramon. We'll take them into consideration when we update the article very soon.

  • RAMON RIVERA from Jacksonville

    Posted on 10/1/2017

    Can you please add to your glossary the new things that make a detector go off like the new proximity sensors on the bumpers of newer models, the side mirrors that warn you of lane departure, emergency braking sensors. Thank you

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