How it Works


The Electric Perimeter Security Fence

attached perimeter security fence

Let’s build a legal security barrier that shocks anybody that touches it, and will trigger an alarm if cut, climbed, shorted, torn down or tampered with. As a bonus, it will also notify us if the voltage falls below a certain threshold.

An electric security fence, or array, can be freestanding, placed atop a wall, or attached to an existing fence. Since most electric security arrays are added to the inside of a chain link fence, that’s the example we’re going to use, but the principles are the same.


Figure 1 – click on the pictures in this article for larger images.

In Figure 1 we see an array attached to the inside of an existing fence. The wires of the array start a few inches above ground level, and there’s a wire every 4 to 6 inches, to a height of 8 or 10 feet. We run the array all the way up because chain link fences are easily cut with a $10 bolt cutter.

Alternate wires are grounded to ensure that anything coming over or through the array receives a shock. If the wires remain in contact with each other for more than a few seconds, it will also trigger the alarm. If a hot wire is cut, the alarm sounds.

This also negates throwing a mattress or other insulator over the array because the fence will short out, which triggers the alarm.

Figure 2 – Animal control arrays are also run horizontally above the ground to prevent digging – click for enlargement

A optional solid cement footer (see Fig. 1), or some rows of heavy debris along the base of the fence can be used to prevent digging under the fence.

Another way to prevent digging is shown in Figure 2. We run the array horizontally for three feet across the ground to prevent predators and other thieves from digging their way in.

In our experience, we have never had a trespasser attempt to dig under an array. They have always tried to come over it or through it. After the first shock, they leave and don’t return.

Another special case is keeping snakes out of utility installations. Our systems are used for this extensively in Texas. Contact us for snake-proofing and other specialized designs.



How It Works – a one minute video


Wiring the Array

Figure 3

We saw in Figure 1 that alternate rows of the fence are hot and grounded.

The next step is that the hot wire from the energizer, out to the array and back again, must be one continuous circuit.

In a monitored electric security array we need to have continuity in the hot wire. That’s how we can constantly monitor the voltage. Figure 3 shows a simple example of this.



Figure 4 – Security Array Wiring Diagram

Figure 4 shows how this is done on a larger scale.

The grounded (green) wires can be bundled and sent directly to ground – the better the grounding, the better the security system.

Having good earth grounds on the array and components is what ensures that anybody that comes into contact with it gets a good, hard zap. This is what knocks them off the fence.

The hot (pink) wire goes back and forth in an “S” pattern, eventually making its way from the high voltage source – the fence energizer – to the Fence Hawk monitor.

This continuous “S” pattern of the energized hot wire is what makes a monitored security array work, and is the key to monitoring the voltage on the fence.


Security Zones

Figure 5 – Eight security zones – example of design and wiring

On larger installations it’s good security practice to split the secured area into smaller segments or zones. This allows dispatching security directly to the area when an alarm goes off.

It also allows you to automatically turn on lights and cameras for that area, if you are so equipped.

Third, it allows you to turn off individual zones during working hours – a front gate, for example – without turning off the entire system.

In Figure 5 the gates are wired and zoned in such a way that the entire system can remain on when the gates are left open. The array on the gates can be turned on or off independent of the rest of the system.


The Fence Hawk Monitor/Sensor – Made in the USA

Fence Hawk computerized PCB

So we designed an improved monitor and sensor we named the Fence Hawk. The state-of-the-art, computerized, patent-pending circuitry measures the actual voltage on the line. When installed, it’s adjusted to the voltage of the array – up to 25,000 volts.

When the voltage falls below a set value and remains that way for a period of time a security alarm is sounded.

When the voltage falls below an adjustable minimum voltage, usually 2,000 volts below the normal fence energizer voltage, a weed alert is generated.

Because the Fence Hawk measures and counts the voltage pulses on the fence, and allows for the occasional random or spurious pulse, it doesn’t generate false alarms.


The Fence Hawk

If the pulse rhythm is interrupted by a nearby lightning strike or a person touching the array, the Fence Hawk is designed to watch carefully, and if the pulse and voltage quickly return to normal, it ignores this.

It only generates an alarm when the fence voltage is lost, or drops below a set level, for a set period of time.

Since installing our first Fence Hawk we’ve had no false alarms, and we’ve never had a perimeter violation when the array was activated and armed – because we believe a system that generates false alarms is worse than no security system at all!

 The Fence Hawk Explained


An Integrated Security System

The Fence Hawk monitor is designed to connect to any alarm control panel. It connects like a motion or smoke detector.

One pair of wires from the Fence Hawk carries the alarm signal, the other pair signals low voltage – the weed alert.

This gives you a fully integrated alarm system, and allows your existing alarm to call the police, trigger sirens, floodlights, cameras, etc., when the Fence Hawk detects an intrusion.


No Alarm System? No Problem.

We have kits and assembled systems with sirens, phone dialers, etc., that make DIY installation affordable, quick and easy. With a phone dialer that calls you directly you won’t have monthly monitoring fees.

We provide free tech support by phone, fax, email, digital photos, Skype, etc.

The Fence Hawk can be used to activate any device. When an alarm or alert is triggered the Fence Hawk closes a set of contacts – a switch – that can be used to remotely activate any device.

We will supply schematics to wire into anything. If we don’t have a schematic for your application we’ll draw one up for you.

Visit our online store for more idea-generating examples, and a broad range of DIY electric security array construction materials.

For more information and technical specifications of the Fence Hawk, click here.

The Fence Hawk installation manual in PDF format.

For photos of a variety of installations that use the Fence Hawk, hover your mouse over the drop-down menus at the very top of the screen – Commercial, Residential, etc.

For a installation quote, or design assistance for a DIY project, please contact us. For DIY assembly tips and tutorials, see the menu items at the very top of the screen.

To purchase a Fence Hawk and integrated security packages, please visit our online store.

We ship and install anywhere in the world.

8 ft. tall perimeter security fence

  16 Responses to “How it Works”

  1. Bobbie, our RSS feed is

  2. Share away, Jaunita. Just give a link back to here, if you would, please. Thank you!

  3. Sure, Anna. You can call or email us with your questions. 813-315-8082 – Jim


  5. we are interested in your products, i think open a shop of equipment for electric fense in colombia.

  6. I am having an electric fence installed on my wall in Salinas, Ecuador. I have my choice of 2 wires, regular steel or aluminum, the aluminum is $100.00 more. I know the steel rusts & the aluminum corrodes. They say the aluminum is better because of the salt air.The yearly maintenance fee is $70.00. Please advise….tnx…..J

  7. Write more, thats all I have to say. Literally, it seems ass though you relied on thee video to make your point.

    Yoou obviously know what youre taliing about, why throw away
    your intelligence on jjust posting videos to yoyr site when
    you could bbe giving us something enlightening to read?

  8. HI JIM,

  9. What is your return policy?

  10. Greetings! I’ve been following your blog for some time
    now and finally got the courage to go ahead and give you a shout out from
    New Caney Texas! Just wanted to tell yyou
    keep up thee good work!

  11. Hi, I have an electric fence that I would like to add your alarm to but I’m unsure what it is I need. I would like the system to notify me by phone and to have the siren and strobe light

    I’m also located in United Kingdom so would like to no the price in GBP and also the shipping charge


  12. Hi, May i ask for your office address and contact numbers in the Philippines? The URL above does not seem to be active anymore. Thank you

  13. do you have distributor in the phillippines if yes can i ask the phn number i would like to purchase one set fence charger

  14. We writing to inquire about the possibility to collaborate and distribute your products and services for Nigerian market.

    We can develop your products and services market in Nigeria; we suppose you will be interested to expand your sales market to Nigeria.

    Please send us your draft conditions and soft copy brochure of your products and services, including training opportunities, spear parts, after sales services.
    Philip Edu

  15. Hello Jim
    I was waiting for your other product Car Zapper. What happened? I can’t find it anywhere.
    Thank you

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