Scenarios: Unrest: Home invasion Pt9: Physical protection: Fences: Perimeter tech

Perimeter alarms:

  • Perimeter alarms can be justified even where you do not have guards, but they cannot be linked to police so you still need your own reaction force of some description nearby.
  • If you are going to have a perimeter alarm then you need to decide:
    • what it will detect, classify, locate and identify,
    • how you will immediately know what to do with an alert,
    • whether to link it to CCTV,
    • how to balance false alarms with sensitivity,
    • whether to have backup power,
    • whether you can have a sterile area outside a fence and perhaps a no mans land inside,
    • what detectors and signalling system.



  • JSP440 classified alarms for the military into four levels from class 1 up to class 4. Class 4 requires backup from other systems such as CCTV, lighting and response force, and is supposed to delay an expert with extended planning, specialist equipment and substitution components. Example are the government AC12M and Almond systems. Class 3 is similar but only supposed to delay a less sophisticated intruder with tools and equipment. Class 2 is supposed to delay an intruder with the necessary basic tools and instruments and limited knowledge. Class 1 is supposed to delay an intruder with little knowledge and limited common tools.



  • Perimeter intrusion detection systems (‘PIDS’) can be made of three elements: detection, assessment, and command & control. Detection can be sensors like radar or fence alarms. Assessment is often electronic analysis to reduce false alarms and increase true positives, but can be CCTV. Sensors can detect image, presence, movement, weight or fence disturbance.
  • PIDS can be built into a barrier through taut, coax or optical fibre wires or electric field signal, or underground seismic, or nearby with pressure sensors such as RF, microphonic, optical fibre or balance fluid tube, or microwave, infared or laser as a perimeter intrusion detection system, but should have anti tamper protection.
  • Vegetation, wildlife and weather will create false alarms. This is accepted as a cost of doing business for external alarms and is why it needs patient monitoring by your response force, multiple detectors to give confirmation, and granular control panels to say exactly where signals are coming from.

Fence disturbance

  • For fence disturbance, usually a laser is shone through a cable and measured at the other end or accelerometers are attached to cable to detect disturbance within a few feet. These alarms can be seen from their junction boxes, sensors and wires with bends covering patches of fence. They are simple as they just go on the fence and follow the terrain, but they need a good fence and can be bridged or tunnelled.
  • Electric field sensors can go on a separate fence, follow the terrain and can handle long runs, but might not be able to narrow down a breach site, need metal object grounding and are subject to interference from vehicles and radio.
  • Taut wires alarms come combined with an electric fence.
  • Buried cables can detect crawling and are covert, but are also subject to interference from vehicles and radio and cannot gauge size of object.
  • Although ruinously expensive due to the sensors and government client list, there is demand for products like SBD terror rated APS Flexiguard which uses fibre optic cable to measure light being jiggled, turning it into a seismic detector. Exactly the same technology is used to detect earthquakes with comms cables under the ocean.
  • A similar product is Agilfence which uses Fibre Bragg Grating to detect strain.
  • Other products may use a couple of piezoelectric microphone wires near the top of the fence like Flexiguard or Harper Chalice’s CPNI rated FenceSecure using VibeWire.
  • Detection Technologies’ Vibrasector uses magnetic sensor cables cable tied to the top of and a metre up the fence to detect changes in magnetism of chain link. The second cable usually goes six feet down from the top or a metre from the ground, or on palisade aris rails. These may ideally need to be programmed with a sensitivity level and to alarm after 2 attacks in 60 seconds for example, and are sold with Gallagher fences combined with their Z10 tension sensors and Z20 disturbance sensors covering runs up to 500, or DT’s MicroTek cut sensors and Vibratek microphonics with sensors covering runs of up to 300-1,000m.
  • Vaylia resell Flexiguard.

Non-fenced based

  • Other detectors not using a fence include PIR, infra red beams, microwave (cigar shaped beams), laser scanners and seismic detectors, all creating a curtain, often used after an intruder has breached a fence, to help reduce false alarms. Infra red and microwave can be line of sight or volumetric but need level ground.
  • You can also buy alarmed anti trespass panels to lay across ground such as ATP Plus from Rosehill.
Rosehill ATP Plus


  • Radar is good for long distance open space and can track targets in all weathers, but only for movement and plays up if used in confined space and is expensive as it needs high resolution range and azimuth. For the right money you can use radar with software to distinguish humans. These need backing up with CCTV using movement detection or content analysis software.


  • Alarms need to be backed by CCTV for assessment, and cameras need to be a combination of wide dynamic range, low light and thermal (low resolution but good with rain). Modern digital camera systems are scalable, high resolution (1080 (HD) or 4K (UHD, check storage, frame rate, low light & lens quality)) and be viewed anywhere. Remember IR illuminators are short range and not good with bad weather. Thermal cameras are good at long distance but with their low resolution need a PTZ to zoom in alongside.
  • CCTV can be linked to analytics which use the CCTV as an alarm to detect suspicious shapes moving suspiciously. The alternative is detector activated CCTV with loudspeakers, linked to a remote video response centre; these are accredited so that police response is possible and they can potentially replace guards, remote guards can challenge trespassers verbally before deciding whether to send a response.
If in doubt, add light

Driveway alarms

  • Much more affordable is a DIY perimeter alarm just inside the boundary.
  • There are videos online how to buy or make trip wire alarms such as the Bisley 12g shotgun alarm mine for £19 (blanks £25, clear fishing line £6).
  • Look at firms like parabeam, detectalarms, ultrasecuredirect and gsmactivate for solar wireless & GSM PIR alarms which can sound a buzzer or a klaxon and light a LED on a radio receiver indoors or can even ring your mobile. You are looking at easily £300 to put a perimeter together. A SBD accredited supplier is MyDome.


  • For a less than lethal discomfort option you could rig up your own makeshift LRAD with something like Dragons Breath SoundBarrier or Inferno (£572 upwards, Micro for sheds, garages etc, Intenso for indoors, Outdoors for perimeters) to blast the eardrums of adversaries at the perimeter using 125db speakers. These are at the top end of the scale for annoyance, but injury takes 140db and neutralisation takes 170db; to neutralise with only momentary pressure, like a blast, needs 250kPA – and that takes some serious pyrotechnics.
Inferno sonic alarm
How much pressure can burglars take?


  • CCTV is mainly for verifying alarms but can also cover area, perimeter, vulnerable spots or can even act as an alarm itself by alerting when a scene changes.
  • You need to decide what quality you want, how it will be monitored (how many screens), whether to have backup power and anti-tamper, how to avoid glare from sun and blockage from foliage, and whether it will link to an alarm.
  • The best signal comes via coaxial cable but unfortunately if you want to avoid excessive cable runs few wireless cameras cover such a distance.
  • The best screen for SHTF is probably LCD due to low power consumption.
  • You need about 3 lux lighting or infrared. Try to avoid asking one camera to cover a scene with brightness range of more than a factor of three.
  • Presumably your specification as a prepper is monitor your home for potentially running intruders on one screen by an amateur for a mutual assistance group reaction force with CCTV alarm as a force multiplier, so you do not need cameras zooming in everywhere or export facility or remote links, and you may not even need recording, at least beyond replay a loop of the last few seconds anyway, but you probably need a decent frame rate like at least 5fps.
  • Choose how many cameras you will use bearing in mind whether you want to monitor distant threats after an alarm in which case traditionally you could accept targets filling only 5% of screen height, or or detect targets without an alarm in which case you need them to take about 10% of screen height, or recognise targets to confirm if they are supposed to be there in which case you need them to take up about 50% of screen height. This can vary depending on resolution and compression and the rules of thumb were based on PAL screens whereas now you can buy digital cameras several times finer. The camera’s field of view depends on lens, sensor and distance from scene. You could add a pan tilt zoom camera for dealing with alerts over a large area. If you need to ID anyone, eg you have a busy mutual support group, coming and going, consider narrower fields of view to zoom in on pinch points like sideways, gates and doors.
  • Ideally get advice from an expert as terrain, weather and lighting affects what will work.
  • The British Standard for CCTV is BS EN 50132.
  • SBD approve CCTV, including some for CNI which specialise in spotting suspicious behaviour and have options to improve on infra red, handle distances beyond the usual 67 metres, stabilise images and follow suspicious characters around between cameras. Such suppliers include:
    • Business Insight 3 with their Davantis Version 70 Daview Analytics Perimeter Protection for long range and sterile zones. There is, for example, a domestic version, the Daview Mini.
  • Infrastructure buyers might also buy a camera management system and alarm management system and would certainly use the software to reduce the number of CCTV operators, whereas a homeowner can just have it send their mobile a video clip, allowing them to trigger a strobe, siren and loudspeaker.
  • CCTV can be enhanced with thermal, infrared or analytics. It can be combined with alarms and at the top end can include volumetric object surveillance such as for museums.
  • As a DIY option, you can get a Spypoint 3G PIR camo cam that texts you movement alerts and images for £240, and wifi overt cameras are even cheaper.


  • Lights can deter intruders, reassure residents, hide guards from intruders via glare and help spot intruders and allow a response. Lighting is to deter through fear of being seen and to let you see; without surveillance to back it up, it just helps the intruder see what they are doing.
  • Mount luminaires inside the boundary, pointing outside. Glare lamps ought to be about five feet high and twenty feet apart. If you have patrols you can silhouette intruders by aiming lights along building walls at pedestrian height on the ground floor, these do not have to be bright, just enough to notice shapes. Do not light up guards or guardhouses. Light up any area intruders would have to cross, using two lamps covering each spot in case of bulb failure. Use bulkhead lamps to fill in any dark spots.
  • Lighting can be controlled by timers, solar cells or switches. Sensitive sites like your home can be further protected with event actuated lighting such as a PIR floodlight. Beware that intruders can manipulate photo sensors.
  • Consider armoured switched and cables to frustrate sabotage.
  • Consider linking lighting to backup power so you keep it even if someone cuts your mains, or go further and set it to all come on if someone cuts your mains.
  • Consider linking lighting to an alarm tamper circuit so you are more likely to know of attempts to sabotage it.
  • Normally for surveillance you want at least a colour rendering accuracy of Ra>60 and 3 lux illuminance per square metre. However, 20 lux is better for gardens, which is streetlight intensity – this is equivalent to a candle a metre off the ground for every 9” square. Buildings regs L ask for photocell PIR lamps no greater than 150W or lamps more efficient than 40 lumens/W (which basically just rules out white sodium or tungsten for continuous use). To stop observers looking through a window needs lighting 7 times brighter outside. Driveways and foliage reflect little light so need brighter bulbs.
  • The old debate about which expensive or orange light to buy such as sodium, halide, fluorescent or tungsten, is over. LED is cheap and white enough, although not as white as tungsten (dim and blows quickly) or fluorescent (which does not last as long as LED either).


  • The torches below are mostly rechargeable searchlights that get hot and quickly power down to below maximum output for cooling off. So you will need a power source from time to time, gloves or some kind of strap to hold it away from your skin, and to buy more maximum output than you need for a walk, for example, so that it remains bright enough after your first minute of turbo.
  • If you want an outrageous searchlight for guards on your estate then look no further than the rocket launcher-sized Japan Cell Alpha1 LED searchlight with 3.1M candela (about 250,000 lumens) – twice as bright as a lighthouse.
  • For garden searches, walks and turning the village green from night to day, there is the Imalent MS18 100,000 lumen (£476) – which powers down intermittently to 25,000 lumens while a fan cools it, or the MS12 ($540) with 50,000 lumens. Turbo will not be needed unless you are searching a farm. If you are not an outdoorsman or search and rescue operator it is probably expensive overkill and you may struggle to recharge it on the run.
  • For gardens and out and about, Imalent have the 25,000 lumens MS06 (£140), which reduces output to cool off after 70s, and Olight do the X9 Marauder for £550, also with 25,000 lumens and similarly dropping to 6,400 after 3 mins, so not obviously worth the triple price tag. These are hefty enough not to be EDC but would stay on charge in your utility room or conservatory for indoor use on low settings or trips or investigating intruders in the garden on high settings.
  • For urban courtyards or indoor use the Imalent MS03 (£93) with up to 13,000 lumens or the Olight X7R at £253 with up to 12,000 lumens should do the trick. On turbo they can temporarily floodlight a garden so are a good EDC all rounder if you do not need a proper searchlight.
  • For EDC you could try the Nitecore TM9K from their Tiny Monster range, with 5s blasts of 9,500 lumens after a few clicks for £155. This can handle virtually anything in short burst except search and rescue, so is a great choice for the car door pocket, get home bag, EDC pouch and kitchen cupboard.

3 thoughts on “Scenarios: Unrest: Home invasion Pt9: Physical protection: Fences: Perimeter tech

  1. Interesting list of high priced gear.

    High-tech has it’s place in the modern world, just not when all the power goes off and lifting up a phone or using your cell phone to dial 999 doesn’t even give you a dial tone.

    I wonder also about those who spend out so much on so little. A lot that is listed is rich mans and commercial thinking and beyond the means of the average ‘guy next door’.

    It’s always been my experience that peppers think and like low-tech.

    On the other hand, preppers who will forage for what they need, LOVE high tech. I know I do. Especially when the grid goes down, high winds, or a lightning storm. 😉

    Ask any professional security firm what they think about, and do, with constant nuisance tripping of alarms. Apart from tying up roving personnel at one site for their entire shift.

    Incidentally, we did a survey of self charging PIR lights and alarms last winter with our prepping group.
    We chose two consecutive days when the ambient light was a little worse than usual. All of the six units I surveyed failed within half a dozen nuisance triggers and none lasted the night. Fine during summer, dire during winter. The overall results from others were close to that.


  2. Thank you so much admin for uploading such amazing content with us your blog is really helpful for me. wish you all the best for upcoming comments. I am also wanted to write blog kindly guide me if my topic is seismic sensor manufacturers then what should I do first and how will I create new and unique content on this topic


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