The hard part of perimeter protection is that there is no comfortable middle ground between missed detections and false alarms. Infrared beams are defeated by obstruction, rain and fog; cameras struggle with lighting and demand heavy compute; distributed fibre sensing is expensive. Piezo cable takes a different route: listening to the ground.
Deployment scenario
Piezo cable is buried in the shallow soil or sand layer as a distributed underground microphone or listening device. Footsteps and tyres excite the ground, and the vibration reaches the cable through the soil as charge. In practice, human footsteps can be detected over tens of metres, and wheeled or tracked vehicles can be distinguished through signal processing.
Typical sites: prisons, detention centres, military bases, airports, borders, power plants and fuel depots. Cable can follow fence foundations or be laid in a serpentine pattern across open ground to form a detection belt.
Achievable performance and engineering constraints
The coaxial cable is waterproof, explosion-proof and EMI-resistant, and is little affected by soil-moisture variation; its rugged construction means it can stay buried for years without corrosion or breakage.
The constraints are equally clear: detection range depends on the soil medium (loose sand attenuates quickly, dense clay carries further), burial depth and surface cover. Rain, wind and wildlife cause false alarms, so pattern-recognition algorithms for event classification are mandatory. These systems are therefore not point alarms but complete networked multi-point plus pattern classification solutions.
Comparison of technical routes
| Aspect | Piezo cable (buried / fence) | Infrared beam | Distributed fibre | Video analytics |
|---|---|---|---|---|
| Concealment | High — fully buried, invisible | Low — posts required | High | Low — cameras visible |
| Weather | Minor impact | Severe in rain, fog and snow | Minor | Poor at night and backlight |
| EMI resistance | Strong — coaxial self-shielded | Moderate | Immune | Immune |
| Cost | Low | Low | High | Moderate (incl. compute) |
| Locating | Possible with segmented network | Broken-beam alarm only | Precise | Possible |
| Main limitation | Soil dependent; natural events need filtering | Easily obstructed or bypassed | High cost and installation demands | High power and compute |
