Technology Explained

Are Surge Protectors Necessary? Here’s What They Really Do

Simon Batt Updated 25-03-2020

People sometimes confuse surge protectors with power strips, but they’re two very different technologies. It’s important to learn the difference, as only one of them will protect your devices from a power spike!


Let’s explore what a surge protector does and how it works.

What Does a Surge Protector Do?

Before we can define how a surge protector works, we need to define what it’s protecting your electronics from—an electrical surge.

Think of the flow of electricity like water running through a pipe. Water moves from one end of a pipe to the other end due to water pressure—water moves from high pressure to low pressure.

Electricity operates in a similar way, moving from areas of high electric potential energy to areas of low electric potential energy. In this case, it’s from one end of a wire to the other end.

Voltage is a measure of this electric potential energy—more specifically, the difference in electric potential energy. When the voltage increases above the norm for at least 3 nanoseconds, it’s called a surge.


If the voltage of the wire is too great—meaning the difference in electric potential energy from one end to the other is too high—then the electricity will surge through. This heats up the wire; if it gets hot enough, it can burn the wire and render it useless.

The surge protector has one job: detect excess voltage and divert the extra electricity into the grounding wire. This is why all surge protectors will have a grounding pin (the third prong on a plug) and all surge protectors must be plugged into a properly grounded outlet for them to work as intended.

What Is an Electrical Surge?

So what causes an electrical surge? Most people think that the biggest culprit of electrical surging is lightning, but that’s not wholly true.

Lightning can and does cause electrical surges, but it’s not as common as other causes. In fact, buying a surge protector to save your electronics from a thunderstorm may not work in your favor.


While good surge protectors can take on a surge caused by a distant thunderstorm, a near or direct hit from a lightning bolt will fry it. As such, the best protection against thunderstorms is to unplug your electronics.

The primary culprits of electrical surges are devices that require lots of power to operate. Depending on the wiring of your home, you may notice at times that your lights flicker when powerful devices turn on and off, such as your air conditioner.

If these devices are switched on, they demand a lot of electricity, which puts a lot of strain on the grid and can cause surges.

Are Surge Protectors Necessary?

Given how surges can happen at any time, you don’t need to worry about when to use a protector; just use it all the time. The real question is what you should plug into a surge protector.


You don’t need a surge protector for your desk lamp or your standing fan, but you do want a surge protector for expensive devices that have intricate microprocessors, like computers, televisions, stereo systems, and media centers. In short, anything electronic and expensive benefits from a surge protector.

Think of it this way: if there was an electrical surge that destroyed all of the devices connected to your outlets, which lost devices would pain you the most? Plug those into a surge protector. It’s better to be safe than sorry.

On an offbeat note, surge protectors can be useful for reducing cable clutter and improving organization 5 Ways to Clean Up Computer Cable Clutter Under Your Desk Cable clutter is one of technology's biggest annoyances. Here's how to organize and arrange the cables under your desk. Read More  with your electronics. All of the cables end up being directed to the same destination, making it much easier for you to handle them all neatly.

Choosing the Best Surge Protector For You

It can be difficult finding the right surge protector for your needs at a good value. What makes a surge protector good? And why are some surge protectors much more expensive than others? Are there any features you should be looking out for?


Let’s break down the basics to look out for when getting a surge protector.

Indicator Lights

Surge protectors only have a limited lifespan depending on how hard they work. Even when the surge protector properly diverts a surge, the protector itself can suffer damage in the process.

As such, one of the most important features is an indicator light. An indicator light will let you know that your surge protector is working fine. Is the indicator light not working? Time to buy a new surge protector.

UL Rating

As for protection power, good surge protectors will come with a UL rating, a rating put out by the independent Underwriters Laboratories that test the safety of electronic devices.

Don’t bother with a surge protector that doesn’t have a UL rating. Also, make sure that the product is a “transient voltage surge suppressor” as many UL-rated power strips still might not offer surge protection.

Clamping Voltage

The clamping voltage is the measurement that prompts the surge protector to start redirecting the excess electricity away from the plugged-in devices. In other words, a surge protector with a lower clamping voltage will trigger earlier, thus protecting your devices quicker.

Any surge protector with a clamping voltage below 400 volts should be good enough for home use.

Joule Rating

This is the maximum amount of energy the surge protector can absorb. If the surge breaches this maximum, it renders the surge protector useless.

The higher the joule rating, the more energy can be absorbed by the surge protector, so a higher joule rating will often indicate a longer lifespan for the product.

For best household protection, you’ll want a surge protector with a joule rating of at least 600.

Response Time

The response time is how long it takes for the surge protector to detect a surge in electricity. A lower value means a faster response. This reduces the time that your plugged-in devices are exposed to the surge, thus protecting them better.

Ideally, you’ll want a surge protector with a response time of 1 nanosecond or faster.

Recommended Surge Protectors

If you’re still stuck on which surge protector to buy, don’t worry. We covered your best options in our article on the best surge protectors The 5 Best Surge Protectors in 2019 Power supply fluctuations can damage your devices. To protect your electronics, you'll want the best surge protector for your home. Read More for every use case, from the budget-minded spender to someone protecting an expensive home cinema.

Defending Against the Surge

All electrical grids experience electrical surges; some more than others. These surges can damage electronics and surge protectors are there to control them as much as possible.

You’ll want to use surge protectors for complex and valuable electronics, such as computers, appliances, and media centers. Keep in mind that it’s not enough to have a surge protector; you need one that’s properly suited to your needs.

Given how power-hungry devices cause surges, it’s a good idea to learn how much energy your PC uses How Much Energy Does Your PC Use? (And 8 Ways to Cut It Down) Wondering if computers use a lot of power? It's time to learn how much electricity your computer is using and how to reduce it. Read More in case it’s a prime culprit.

Related topics: Electronics, Hardware Tips, Surge Protector, UPS.

Affiliate Disclosure: By buying the products we recommend, you help keep the site alive. Read more.

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  1. Richard
    October 25, 2018 at 3:47 pm

    I purchased what I believed to be a good solution of surge protection and battery backup with a six socket outlet APC device. Unfortunately, the first lightening we had and I noticed that our lights and the PC was off. I thought the battery backup was to keep computers from a forced shutdown, but no. If lightening strikes and your surge protector is in the same device, then youve probably paid over the odds for your solution. In future I will have a surge protector into which is plugged my battery backup. If the faster acting device is the surge protector then that's probably going to spare your other equipment from total surrender! It does appear that the amount of spikes or surges a device can cope with is more a guide to its lifetime than how fast it is. It needs to be faster than the cheapest thing in the supply circuit. Just because your computer has a power brick does not mean it doesn't need extra protection. How would you like to have to buy a power brick for your out of warranty equipment? No. I found out when a power brick for my Clevo based gaming laptop comes in at a whopping £132 (UKP)

  2. Bernardo Sanches
    October 24, 2018 at 8:30 am

    One of the most popular surge protectors/Power Distribution Unit (fancy name for multi-plug strip) in the music industry has a brand name of Fuhrman. DO NOT BUY Fuhrman surge protectors or power conditioning units. All that talk of joules, & clamping voltage & response time means nothing if the the surge protector doesn't act when there's an overload. I had an overload. I didn't plan it, a piece of electrical gear failed and shorted. The Fuhrman AC Line Conditioner tasked to protect the AC gear connected to it exploded. It's in a metal case, so nothing blew out of it, just a fantastic flash of light, a loud noise, smoke, upstream circuit breakers threatening to trip, the lights get real low, and the AC device connected to it fails CATASTROPHICALLY and CATCHES ON FIRE. No joke, no lie. Okay, so that's real bad since the whole point of the AC line conditioner was to handle the AC it distributed. What was worse was Fuhrman's customer service reaction. They did not care. They cared enough to email me to tell me they didn't care, but that was far as their concern went. If nobody died, & the place didn't burn down (it didn't) & I wasn't threatening to sue, they didn't care. I explained the fire, the explosion, and I offered to send them the offending unit for analysis. They didn't want it, & didn't care about any of the rest. I'll buy APC & Tripp-lite & others, but NEVER will I buy another Fuhrman product under any circumstances. They are dangerous, both the equipment and the staff.

  3. Reuben myers
    August 12, 2018 at 11:25 am

    Thank you for writting this i have lerned that i should have a power surge for my xbox 360 it started stop working and i thault it would be fine if i didnt yous a power surge iwas going to you a reguler cord thank you :)

  4. Always Learning
    February 29, 2016 at 2:54 am

    The most common surge protector uses MOV's (Metal Oxide Varistors). They work on a voltage threshold and when turned on, begin to divert the surge energy to both the Neutral and/or the Ground (depending on whether it's a triple mode L-N, L-G, N-G, or just single mode L-N).

    Electricity at 50/60 Hz has a low impedance (resistance) return path via the Neutral, but at surge frequencies (3 KHz to 350+ MHz), the return path can be anything but easy and if it's difficult (high impedance), the surge will seek another path, often times through the very electronics plugged into a surge protector.

    By way of an analogy, consider a hand gently breaking the surface tension of water & freely moving underneath the water. This is how it is for electricity. Now take the same hand, slam it as hard as you can into the water & you’ll encounter a lot of resistance, perhaps it will feel as if you hit a brick wall. This is how it is for surges. The water is analogous to the house wiring. At some frequency the surge hasn’t got a chance & will seek another path perhaps damaging our electronics in the process. That’s why spikes or transients which are often measured in billionths of a second are least likely to find their way, & often zap our electronics instead.

    Surges can damage your electronics almost immediately or over time (a bunch of smaller surges). Here's another water analogy: when hot water (surge energy) is poured onto an ice cube (your appliance or electronics), the ice cube is still there until either large amounts of hot water are poured over the ice or a cumulative number of small drops are poured over the ice. Eventually the ice melts & so will your electronics.

    Now for the really bad part, those "all-in-one" surge protectors that offer to protect coax (cable TV, satellite, antenna, internet), phone (telephone, DSL), network as well as AC outlets all share a common ground. Once the surge is diverted by the MOV to the ground, the ground wire can be at several thousands of volts for the duration of the surge and since those all-in-one protection circuits operate at different voltage thresholds, most often the things connected to them on the other end are damaged, yet the surge protector continues to work.

    If you think, why not just get a "Whole House" surge protector installed in the mains electrical panel, there are a couple of problems with those as well: (1) The leads need to be very short. Even 12-14" of wiring (which is twisted) adds up to 350 Volts to the "let-through voltage", so if the box states 600 Volts "Let-Through" the real "let-through" can be closer to 1000 Volts - enough to damage a lot of electronics in the house, so "Whole House" might help, but it still requires more surge protectors in the house and unfortunately the ones that use MOV's are not the answer either.

    Lastly, a technology that is more than 26 years old called "Series Mode" works differently from MOV based technology, namely it slows the surge down, stores it as energy and releases the surge a few volts at a time on the Neutral wire. Recall the water analogy? If the hand (surge) moves slowly, it can penetrate the water (make it's way back to the mains panel) without incident. They are made by Zero Surge, Brickwall and SurgeX but cost from $140-$160+ new or from $30-$60 used or new old stock on the most popular auction site. You come out much further ahead with series mode because the surge is actually dealt with instead of diverted.

  5. Orest
    November 25, 2015 at 1:38 pm

    I think these devices are useful but if we utilize it right! For example, as I guess it is important thing for big companies! It is nice protection!
    And in the same time you are totally right about electricity consumption of such devices! I have always been scared about lightnings and we decided to buy overvoltage system to protect our equipment. We bought Dehn ( as you see it is not very cheap!) now I have dilema: to feel save or to spend more money on utility bills? Because last time it became very high! And i reckon, it should be some method how to reduce it, but it has been unknown for me yet!

  6. Anonymous
    September 11, 2015 at 7:28 am

    There never seem to be enough places to charge all the electronic devices in the house. I have been looking for a desktop AC outlet solution like Ankway for awhile,finally i got it from Ankway they makes a lot of sense. The power center has two AC outlets and five USB ports. It has built in surge protection & a circuit breaker. As for the USB ports are smart and can handle up to 2.4 amps. The smart ports can automatically figure out the amperage that is needed for that device and only give it that much, it will save the balance for the other ports. The five USB ports can handle a total of 8amps. You will see a blue LED light and that is your indication that everything is working properly. There are plenty of power strips on the market but this one is versatile and looks good on my desk. I am glad to know that they have made safety an important factor in their power center.

  7. Malcolm
    January 24, 2014 at 6:21 pm

    I recently found out that you can buy whole-house surge protectors. In the UK I found one for £46 and it fits easily into a spare slot on the mains consumer unit (main fuse board)

    That means you whole house is protected - every single circuit - lighting, sockets etc for not much more cost that a good quality six-outlet surge protected power strip. And, unlike most surge protected power strips, you don't throw it away if a power surge occurs, you just have to reset it!

    Most people probably plug their laptop into one of many sockets around the house and with a whole house surge protector all those sockets are protected too - as well as lighting and any other circuits.

    You can also get whole house surge protectors that protect against lightning strikes too but I read you only need this (type 1) surge protector if you have overhead power cables feeding the house and/or you have a lightning rod fitted to your house. As I have neither, I will be going for a type 2/3 device.

    Similarly, if you have overhead telephone lines feeding your property these need to be protected against lightning as well as they can destroy any equipment connected to them.

    UPS (Uninterruptible Power Supplies) may also protect against power surges and the one I am thinking of getting, even offers a guarantee against lightning strikes and can also be reset after a power surge:

    • Dave
      December 1, 2016 at 9:17 pm

      Don`t forget tv aerials as well. A surge protector should have a facility to run your coax through to protect your tv.

  8. wilhelmina
    January 9, 2014 at 1:45 am

    I am sorry to butt in but I am looking for an outlet extension that has outlets on the sides, for behind my TV. A lot like the Side Socket you see advertised.
    It is called a surge protector, but is it any good? Is it possible to get a surge protector that has outlets on the sides like this?
    I want to plug in my TV, Nintendo Wii, internet modem and internet router. Also my DVD player but it is only used rarely. Is a surge protector even necessary?
    Thank you in advance for any advice.

  9. Bytendorp01
    November 20, 2013 at 4:23 pm

    If you were to loose the neutral on your house and have a potential of 240 volts to an outlet would 240 volts smoke a computer? Yes , so how does the computer that is plugged into a surge protector with a clamp of 300 volts get saved? Im confused.

  10. Ole Tange
    August 13, 2013 at 10:48 am

    Neither I nor any of my friends use surge protectors and have never lost any device due to surges.

    Could this be due to the fact that we have excellent wiring (e.g. the light never flickers if we turn on power demanding devices) and an electricity company that has an electricity drop out at most 1 time every 5 years?

    Can you elaborate a bit more on what causes the surges? Is there a way to measure how many surges you have?

    • Joel Lee
      August 16, 2013 at 6:03 am

      The excellent wiring might have something to do with it. Surges don't have to be big flashy events, though. Small surges that happen every once in a while can gradually deteriorate the quality and condition of your electronic devices.

      I'm not really qualified to elaborate on the causes or measurements involved with surges.

  11. Paul V
    August 11, 2013 at 7:16 pm

    Great article, I'm buying a couple Tripp Lite TLP606 next week.

  12. Meidimi S
    August 11, 2013 at 8:45 am

    i once had to replace my mother board because a lighting storm fried it up. i don't think a surge protector would have helped but i find them useful

    • Lisa O
      August 11, 2013 at 4:33 pm

      My UPS was fried the week we needed it the most. A week of very frequent blackouts and my mainboard was fried, along with other small things. No joke indeed. Surge protector will replace power strips after this.

    • Dave
      December 1, 2016 at 9:18 pm

      It would have.

  13. Geoffrey Richardson
    August 11, 2013 at 12:24 am

    Maybe I have been lucky, but I have used surge protectors for at least 20 years and have survived lightning storms, power surges and sudden blackouts due to fallen branches across lines and strikes on sub-stations without losing any equipment.
    Having no special knowledge of their workings, this article was of great interest to me. Thanks, Joel.

    • Joel Lee
      August 16, 2013 at 6:00 am

      It's great that you went 20 years without a problem. Hope you didn't just jinx yourself, ha!

  14. Steve
    August 10, 2013 at 4:15 pm

    Don't just protect your mains connection, surges can also arrive via the telephone line. When buying a surge protector or a UPS, look for one that will protect your incoming telephone signal(s) as well.

    • Joel Lee
      August 16, 2013 at 5:59 am

      Good point. Not only the telephone line but also the ethernet cord!

  15. Michael F
    August 10, 2013 at 12:26 pm

    Why does nobody speak of Noise Filters on surge protectors anymore? I see it mentioned occasionally in the specs, but it's a lot harder to spot than back in the late 90s when I used to sell them regularly in retail.

    Line Noise occurs when other devices on your electric wiring generate, well, noise. The best example is an old analog television when you'd run the vacuum cleaner and suddenly there'd be static or lines and stuff. The noise filter in a surge protector would filter that out and protect your device from that interference.

    • Joel Lee
      August 16, 2013 at 5:59 am

      It might be because analog is a thing of the past and everything is moving towards (or has already moved towards) digital. I don't think noise really interferes with digital, but I could be wrong.

  16. GF
    August 10, 2013 at 9:29 am

    The recommended surge protectors are rated 600...790 Joule. Can it be true???
    Such cheap surge protectors are based on a disk varistor. In the best case, I mean a varistor 20 mm diameter, the maximum Joule are 100...200 Joule.
    How can those surge protectors be rated 600...790 Joule?

  17. Leland W
    August 10, 2013 at 7:47 am

    If you want better protection but no battery backup I would go one better and get an AVR (automatic voltage regulator) which has capacitors in it to even out the power whether there is a sag or surge in power. The sags are the thing that tend to kill high end electronics like computers. Surges of course too especially with lighting. However for a computer a good UPS with AVR is the best choice.

    • David Payne aka The Computer Guy
      August 10, 2013 at 8:59 am

      AVR'S are good for spikes and blackouts from the electric company, which happens alot down here in Florida, The Lighting Capital of the world, But nothing, absolutely nothing can block or stop a direct hit from lightening on your computer. I love bad weather, every time it rains, I make money. The sad thing is it is so simple to prevent. Unplug or pay.

      • Lisa O
        August 11, 2013 at 4:31 pm

        Indonesian cities, like Pekanbaru, can compete with Florida for blackouts rate. It can happen even in the sunniest of days. Much better lately, tho.

  18. Steve Conant
    August 10, 2013 at 7:25 am

    I guess I am surprised that anyone is having (not protected against) electrical events with their electronics. More surprised that this got to me through makeuseof. What is next week... backing up 3.5" disks?

    • Shane E
      August 10, 2013 at 2:48 pm

      Glad you know everything. This article was useful for me. I didn't know what clamping voltage was, etc. Also, a lot of people know to put a surge protector in front of the PC or TV, but as this article points out kitchen appliances often need them too. I opened my new fridge one morning to be greated by a bunch of flashing lights on the control panel. The service tech told me to put it on a surge protector and it likely wouldn't happen again.

      • Joel Lee
        August 16, 2013 at 5:58 am

        Agreed. There's a difference between knowing THAT you should use a surge protector and knowing WHY you should use a surge protector and HOW to choose a good one. A lot of people don't even know the difference between an outlet strip and a surge protector, so I wouldn't call this stuff common knowledge.

  19. Merlyn
    August 10, 2013 at 5:41 am

    Great Info, thank you. However, this info would be useful 6 months ago...Had 2 computers condemned by lightning strikes last year and bought a Belkin . Happened to be the only brand available in the market and costs 3 times the price of the Maruson. Has 6 outlets. Imported from USA.
    More brands are available now from Korea, Taiwan, Singapore. Belkin does give a guarantee and claims up to 20k USD for this model. How about the ones listed here?

  20. David Payne aka The Computer Guy
    August 10, 2013 at 3:41 am

    nothing can protect you from a direct hit of Lightning and with that said surge proctors and save you ALOT of money. But, if it is storming hard unplug or you may have to end up buying new equipment. The most common thing that people forget to unplug, on their computer is the Lan cable.

    • Sure
      August 10, 2013 at 4:57 am

      Exactly, must unplug electronic devices and specially, Lan Cable while lightning and storms. I learnt a lesson from of this painful experience in the past just couple of months ago. :)

    • Joel Lee
      August 16, 2013 at 5:55 am

      Yes, lightning is just too powerful. It might be an inconvenience to unplug everything whenever it storms, but that's the best way to protect your electronics!

  21. Surgey
    August 10, 2013 at 3:25 am

    The best protection against electrical surges are UPCs. Those devices are powerful or smart enough to protect electronics from lightening. Top of the line UPCs generate graphs of electrical surges and then use algorithms to disconnect from the grid when surges peak.
    A good UPC is expensive so the cheap alternative is to daisy chain surge protectors. The more surge protectors you have connected, the more protection you have (not to mention outlets)! I personally connect at least two surge protectors together for every device.

    • Achraf A
      August 10, 2013 at 4:43 am

      If you use more than 3500 W from a single outlet connected to multiple surge protectors, you are in real danger.

    • Shane E
      August 10, 2013 at 2:43 pm

      I could be wrong, but you may want to do a little research on that. I've always read that daisy chaining surge protectors was a no no because it gives them a less direct path to ground.

      • Joel Lee
        August 16, 2013 at 5:54 am

        I have no idea what the right answer is here, but this one sounds the most reasonable to me. Time to do some research.

  22. Eric B
    August 10, 2013 at 3:19 am

    We lost some electronic equipment that was on a surge protector that was supposed to be good. The only equipment that survived was what was plugged into a philips SPP7345WA Turned out we had a bad "negative?" I think it was. Caused the whole house to surge off and on. I wish I could still find these. They are the best surge protectors we've ever had.

  23. Mike C
    August 10, 2013 at 2:53 am

    This is why I have a power conditioner. Long live Furman.

  24. Lee
    August 10, 2013 at 2:52 am

    This may sound a little dumb, but are surge protectors the same as regular power strips? By power strips I mean the white bars that have multiple outlets with an on/off switch on one end.
    It seems like a surge protector would need more room, so I'm assuming regular power strips just connect multiple outlets together to make more outlets than is available in the wall, and thus wouldn't provide any more protection than just plugging it into the wall. Is this right?

    • Achraf A
      August 10, 2013 at 3:58 am

      Unfortunately, yes. Those "white bar" power strips just link up a few more outlets in parallel to the main power cord. In Contrast, a surge protector has actual circuitry to let it fire-up the protection if a surge is detected, in less than 1 nanosecond, lower than what it takes a voltage change to become a surge, which is 3 nanoseconds.

  25. Jamie
    August 10, 2013 at 2:32 am

    The way most surge protectors are linked internally, the surge will fry the outlet closest to the power cord first. The second outlet provides a little more protection because the surge has to go through two levels of protection. Expensive or more sensitive devices should be furthest from the surge protector power cord. Theres no reason not to use one if you value your electronics.

    • Joel Lee
      August 10, 2013 at 2:41 am

      I never knew that about the "frying the closest outlet first." It was always something that I thought might be true, but to hear someone else verbalize it and confirm it is quite interesting. I have a few surge protectors that I need to rearrange now!

    • Serra Stone
      August 11, 2013 at 6:57 pm

      I also didn't know that! But as seen in my pic above your post, it looks to be true. It fried the outlet closest to the power cord!

  26. Serra Stone
    August 9, 2013 at 9:33 pm

    As seen in this picture, yes you do need a surge protector! If I wouldn't have had one, a huge amount of money in computer parts would have been fried!

  27. Matt Smith
    August 9, 2013 at 9:14 pm

    A friend of mine recently lost a television, a stove and a few other items to a power surge. The surge was so powerful a power meter at a house near to him blew up. I don't know if the cause was ever determined; it happened on a sunny day with little wind and no reported accidents.

    The story had a happy ending, though, because home owner's insurance covers this sort of thing.

    • Joel Lee
      August 10, 2013 at 2:21 am

      Blown up power meter? Holy crap! That's pretty weird, especially since it was on a sunny day without accident. Not sure if a surge protector would've protected against that, but good to hear that insurance covers it!

    • Lisa O
      August 11, 2013 at 4:26 pm

      That sounds like something out of urban legend, the kind would like to see. He's a lucky guy, your friend. Imagine if he didn't have that kind of insurance.

      February 26, 2017 at 8:34 pm

      About 3 years ago,our sears stove went out. We called Sears and they checked our stove and said the electronics were all fried. our cost for exam $45.00. Estimate to fix stove $600.00. I did a little research and found that if I unplugged the stove for a couple of ours and plugged it back on, the computer would reset and that ,would take care of the problem. I did that and surprise, my stove was on again. I saved $600.00.Thereafter every time my stove went off, I flicked the fuse box for a couple of minutes and my stove would come back on. Suddenly it hit me. The surge protector !!! Tomorrow I will buy a surge protector.
      SEARS, WHAT A SCAM. $600.00.