Electric fence zone planning: how long should one zone be?
A practical zone is 80–200 m because that is the distance a guard can verify within a 3-minute response. A 2 km line therefore needs 10–25 zones, each tied to a camera preset and a named access point; one long zone turns every alarm into a site-wide search.
A perimeter alarm is only useful if someone arrives at the right place in time. That sounds obvious, yet zone plans are often drawn from the cable drum: equal lengths, neat numbers, no relationship to how a guard actually moves through the site.
This note describes a response-first method. It works for pulse, tension, fibre, buried cable and beam systems, because the logic is about people, not electronics.
How long should one zone be?
Start from the response time, not the technology. If the guard needs four minutes to reach the far end of a zone, and can walk 80 m per minute on a clear path, the one-way distance should not exceed about 320 m — and that is before allowing for gates, stairs or vehicles. On most industrial sites, 80–200 m per zone is a practical range; on a compound with vehicles, 200–400 m is possible.
The sensor also sets a limit. A pulse or tension host normally covers one or two zones, and a long zone has more cable, more joints and more places for a fault. A 500 m zone is technically possible and operationally poor: the guard still has to search 500 m.
| Response model | Typical zone | Break at | Watch-out |
|---|---|---|---|
| One guard on foot | 80–120 m | Corners, gate posts, building lines | Two-way search at corners |
| Two guards, one per side | 120–200 m | Natural split between patrol areas | Shared alarm ownership |
| Vehicle patrol | 200–400 m | Access roads and gates | Vehicle cannot enter the sterile strip |
| CCTV verification only | 80–150 m | Camera preset boundaries | One camera cannot cover two directions |
Where should zones break?
Break at physical features the guard can see: corners, gate posts, building lines, changes in wall height, culverts. A zone should correspond to one geometric edge, not a distance measured on a drawing. If a zone crosses a corner, the guard has to look both ways and the camera preset cannot cover both.
Avoid breaking in the middle of a long straight wall unless the response distance requires it. A break needs a terminal post or a splice, and every break is a maintenance point. Fewer, well-placed breaks beat many arbitrary ones.
How do gates change the zone plan?
A gate is not a zone; it is an opening with its own response. Terminate the fence zone at a fixed post beside the gate, protect the gate leaf with a contact, and cover the pedestrian gap with a separate beam if needed. If the fence zone continues across the gate, every delivery becomes an alarm.
Vehicle gates need a loop or a contact, not a beam across the roadway. A beam at the gate should cover the gap beside the vehicle lane, where a person can walk through while the barrier is up.
How many zones can one guard handle?
The control system may support 128 addresses; a single guard cannot. Count the zones the guard can reach within the site’s response time, then add the time needed to verify and report. If the answer is six zones, the perimeter should not be divided into twenty.
For large sites, split the perimeter into response areas with their own guard or camera cluster. The control room can still see one map; the response is organized by area, not by a single patrol route.
What should a zone map contain?
At minimum: the site outline, every zone boundary, the zone name used by the guard, the device address, the camera preset, the nearest access point and the response route. Add the cable route and the earth electrode for maintenance.
Print it and walk the site with it before commissioning. If the map does not match what the guard sees, the map is wrong, not the guard. Correct the drawing and the zone names before the system is handed over.
How do you test a zone plan before installation?
Do a paper walk: trace the guard’s route on the plan, time each leg, and mark the points where the guard would have to stop, open a gate or wait for a vehicle. Then walk the site at night with a torch. Most zone plans that look reasonable in a meeting fail at night.
If the plan cannot be walked at night before installation, plan for a commissioning adjustment. Zone boundaries that looked good on paper often need one post moved after the first real patrol.
