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Review: K40 Electronics RLS2 Radar Detector with GPS marking


There is nothing like coming home from a long day of work, so tired you feel as though you can face plant into the soft cloud that is your bed and float away. Your attention is well on the road and you have your eyes monitoring all the cars around you. No swerving or heaviness in the eyes thankfully but that loss of energy causes you to miss one important variable: How fast are you going?

Now you make it home without ever shedding a thought about it. Or, you might have an unfortunate reminder from an officer waiting around the corner with a ticket in his or her hand. None of us want this and although you shouldn’t be speeding, you probably would rather have a less expensive poke in the arm vs a confrontation with the law. This is of course possible with a reliable radar detector that can warn you of the presence of a nearby officer who is scanning drivers as they go by; and a reminder to yourself to look at your dashboard and pay attention.

K40 Electronics has an answer for this. With their RLS2 radar detector with GPS location marking, you can see the law before they see you. As an added bonus, it comes with lots of extras to really make you feel on top of the technology evolution of things, giving you a much calmer state of mind as you drive. If you have ever had one before, then you know what I mean.

Focusing first one what separates this from most, is the GPS. The RLS2 has built-in GPS that allows you to mark your location for things like speed traps, red light cameras and school zones. This way, the next time you come near this area, it will warn you so that you will be reminded of what’s ahead. There is a competing brand that takes this step further by integrating their detector into their own national database of locations so you not only get yours but the locations found by others, but K40 hasn’t quite gotten there yet (and the competing unit is also slightly more expensive). It does however function well for what it does as knowing what’s ahead before you even get there does wonders for certain locations where red light cameras and speed traps run amuck–like California.

Once you have reached a location where you feel you need to mark it for the future, you would press and hold the mark button and go from there. Next time you approach it, it will warn you that it is ahead and you will be safe from making a common mistake of forgetting, and blowing past that school zone–I think school zone is the best example because honestly, there is no excuse for running a red light.

Of course, the question that has the most weight is “does it work?”, and that answer is yes. It works quite well actually. We have spent the last week driving around to known areas where we have seen plenty school zones and police traps. We do not have red light cameras here, but we marked certain locations as though there were, just to make sure we get the full effect of things. It effectively warned us everytime we came close to the area. It would be nice to have a network of marked locations as mentioned before (a recommendation to K40), but it did its job well in keeping us all safe (who have had it in our cars).

For radar detection, it supports all of the current bands including X, K and KA, while also supporting laser. This is common for most any detector. What defines a detector is how well it recognizes those bands at a distance, giving you plenty of notice. The RLS2 is above average in detection although not perfect. We took to a number of corners where we knew an officer was hiding, changing up the detectors each time. In our tests we used the RLS2 (K40), as well as a Passport 9500ix (Escort) and a SPX 6700 (Cobra). The results of every location were nearly the same. The RLS2 did circles around the Cobra unit, where the Escort unit came in as more sensitive than the K40 unit. Although it didn’t do circles around it, the Escort did pick up the officer slightly sooner each time. The fact that they were close places the RLS2 high in the ranks for sure.

There was a few points where it didn’t come in where we expected it to on accuracy, but that could have also been due to uncontrollable variables, such as what the officer was doing at that exact moment.

It does pick up a bit of unneeded X-band once in awhile. Nothing near as bad as the low-priced alternatives that are out there of course, but enough to notice that it wasn’t filtering all of the false positives. I remember some years back I had an old Cobra. It was my first detector that I had ever owned. No matter what I did, every time I came anywhere close to a convenience or grocery store, that thing would light up because of the automated doors to the store. I felt that every 2 minutes that unit was going off about something. None of us got that feeling about the RLS2. It is a little more active than something like the Passport unit, but it is lightyears ahead of those older models a lot of us are familiar with.

There is also filtering for K-band false positives that can be caused by nearby vehicles. You find more and more now that cars are being fitted with safety that help to warn the driver against cars suddenly stopping ahead of you or hiding in your blind spots when you are about to switch lanes. The same technology is used for parking assistance to assist in things like parallel parking. All of this uses radar to accomplish these wonderful perks and all of these could cause havoc on your radar detector in the future. K40’s detector has a built-in filter that helps eliminate any false positives that could be caused by such technologies. Although we haven’t seen this just yet with older detector models, I can see how this could become a problem in the near future.

IMG_6138-closeupAll of your controls are located at the front-top of the unit. A common place to find them and they are very straight forward.

  • Mark button: immediately on the left which controls your option of marking the location as discussed for things like speed traps and it can also mark to mute the location to in case you know it’s a false positive.
  • Quiet Ride button: which is for silencing alerts when you travel under a set speed. You can define this speed with this button (ie, if you travel 25 mph or less, it can mute any notifications from bothering you because there is little to no chance that you will be speeding). You can adjust the set speed between 5 and 75 mph.
  • Mute button: located dead center of your buttons, it is used to silence current alerts. You can choose to mute for 30 seconds or 5 minutes depending on if you press it once, or press and hold it for 3 seconds.
  • Up/Down buttons: up and down arrows which are used for adjusting settings, these buttons are located above and below the mute button.
  • Filter button: this is used to adjust your alert sensitivity. You have Highway, City or Filter as your options. Highway is your most sensitive of the three, City is for driving around town (reduces your X-band sensitivity) and Filter eliminates X-band completely and reduces the sensitivity of the other bands.
  • Dim/Menu button: This allows you to set the brightness of the screen by pressing it once each time. You can access the menu to adjust all the settings with, by pressing and holding the button until the unit says “menu”. You then use single presses of the button to flip between menu options and the up/down arrows to adjust the various settings.

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IMG_6141On the left-hand side of the unit, you find your input for power and a slide-wheel for turning the unit on and adjusting the volume. This is actually nice as some units are on as soon as you plug them in. This means if you have an “always-on” outlet in your car, you have to remember to pull the plug each time you turn your car off (and plug it back in everytime you are about to take off). The RLS2 can remain plugged in at all times and you can simple turn it on by rotating the power wheel and you’re done.

Some of the many settings include your current speed and direction (compass), which are both enabled by default. This is a good feature we’d like to see all detectors have, allowing you to see a digital readout of your speed and direction right there on the screen. We found that the direction was quite accurate and the speed was accurate for the most part, with about a 2 mph margin of error. You do have to have GPS connected and working for the information to display, so in unique situations where you may be driving in an underground tunnel or something, you may lose this feature until you have a mostly open view of the sky again.

It does talk to you so that you have something more pleasant than just a bunch of tones bugging your ears all the time. Of course the tones are there as well, but for some reason, voice always helps sooth that (and it impresses your passengers as they look around to figure out where that voice just came from).

Inside of the box, K40 gives you both a coiled cable for short distances and a straight cable in case you need to reach something further or would like to run the cable in a clean manor to reach the mounting point with. I personally like to run it around the window so that there aren’t any cables hanging down from the unit. It looks much cleaner and professionally installed when you do it this way. This is all user preference but also a great perk since you sometimes have to buy the straight cable as it isn’t always included in the box with some of the competing brands.

The mount that attaches it to the window with features 3 points of attachment where suction cups are used. Due to the light weight of the unit, it stays on the window quite well without falling off. In our tests, we didn’t experience any troubles with this. Plus, since you have three separate suction cups, if one were to lose it’s grip, you still have 2 more holding on for dear life, allowing you to respond vs it simply falling to the floor. We even took it to a casino parking lot here that is notorious for far too many speed bumps, and didn’t have any troubles.

It also comes with an extra fuse for both cables in case you blow a fuse–which should be unlikely for the most part unless your electrical system takes a hit from something (let’s say you burn up an ignition coil that causes a bad surge in things). You also get a quick reference guide/card (laminated) to keep in your car for easy deciphering of the menu options.

We reached out to K40 to determine if they bake test their detectors for temperature sensitivity and durability. We started doing this a long time ago because we had a Beltronics unit sustain damage due to being in direct sunlight exposure for a long period of time. The damage caused the audio to no longer function (our theory was that the solder points couldn’t withstand 100-120°F heat. K40 responded back to us with an answer we were hoping to hear. All of their units are tested and can operate without any troubles in temperatures between 10°F and 165°F. They explained that the plastic material they use will not begin to give out until temperatures of around 210°F.

Last but not least, I wanted to quickly highlight their ticket guarantee which is nice. Within the first 12 months of owning the detector, if you are issued a ticket while the unit was properly being used (and the driver was not inebriated in any way), they will cover the cost of that ticket (except for school and construction zones). This means they are quite confident in their product and back it well.

The one thing to keep in mind though, is that this doesn’t give you a get out of jail free card to act however you’d like on the roads. Always remember to drive safely and prevent from speeding. These detectors are a reminder to pay attention and not an excuse to act like a jerk. Dangerous driving puts others around you at risk as well and you don’t have their consent to take their lives into your hands. Drive safe, drive smart!

Our Conclusion

It is a nice detector and does a good job warning you before you find yourself in trouble. It isn’t as accurate as a few others out there, but it does come in as slightly more affordable. We believe the GPS functionality needs more though. It needs to come pre-loaded with a database and/or support updating it via online. GPS works great for what it is, but due to the price tag, there needs to be more. Accuracy could be enhanced a tad and GPS improved on, else a good drop in price would be needed for a perfect score. For what it is though, we decided to give it a 7 out of 10. Performance-wise, it does great and it features a lot of options we would expect from an advanced unit. Just try to remember that this doesn’t mean you are invincible and should drive around like a bat out of hell.


Our Rating

7 / 10 stars           

Average Price*


*Average price is based on the time this article was published


Additional Images:


Detects all North American approved police radar frequency and radar gun:

Operating Frequencies 10.500 – 10.550 GHz (X-Band)
24.050 – 25.250 GHz (K-Band)
33.400 – 36.000 GHz (Ka-Band)
830 – 945 nanometers (Laser)
Power Requirements 11.0 – 16.0 Volts DC negative ground
170 mA typical standby
Dimensions 5.11 in. L x 2.86 in. W x 1.39 in. H
Weight 5.1 oz.


Three Filter Settings:

Level/Mode Sensitivity Recommended Use
1. Highway
(factory default
Detects all North American police radar (X, K, and Ka-Band) and laser signals at full sensitivity. For highway travel or in any area in which you are unfamiliar with the types of radar used.
2. City 50% reduction in X-band sensitivity. This is because it is the most common source of non-police radar signals. K, Ka, and Laser will remain at full sensivity. When traveling in an urban area with minimal non-police radar signals.
3. Filter Eliminates X-Band detection completely. Reduces
K and Ka-Band sensitivity by 50%. Laser detection will remain at full sensitivity.
When traveling in a congested traffic area with a high concentration of non-police radar signals.

Programmable Features:

  • Voice Type – Male / Female
  • Audible Voice – Voice On / Voice Off
  • Wake Up – Wake Up Long / Wake Up Short (abbreviated start-up sequence).
  • Speed Displayed – Speed On / Speed Off – for mph/kph on screen.
  • Compass Heading – On / Off – directional heading on screen.
  • Traffic Sensor Filter – On / Off – Filters k-band traffic flow sensors.
  • MPH / KPH
  • Automute
  • Quiet Ride – Set minimum detection speed from 5 mph – 75mph / 10 kph – 120 kph
  • Speed Monitor – Set to alert when a preselected speed is exceeded.
  • X-Band – On / Off
  • K-Band – On / Off
  • Ka-Band – On / Off
  • Laser – On / Off
  • Mute Locations
  • Alert Locations
  • Factory Reset


Radar Receiver Type – DSP Datadyne Technologies

GPS Receiver Type – SiRFstar III

Display Type – Full Dot Matrix Display

Signal Strength Indicators – Audible Geiger and numeric signal strength indications

RDD Guard – Protection from Radar Detector Detectors


Are you a manufacturer or distributor that would like us to test something out for review? Contact us and we can let you know where to send the product and we will try it out.

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About Author

Designer, Editor and Product Reviewer
Poc Network

Ryan is an avid gamer that spends most of his time either commanding teams on the Xbox One or out on the grass kicking the soccer ball around when others are willing to take the challenge. He comes with a bachelors in electrical engineering and a hobby in the installation of advanced audio-video environments.

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