Siva Pulsed wire mesh system offers the most reliable fence protection by detecting intruders trying to cut through the fence. It is suitable for most kinds of fences and can be easily installed.

PRINCIPLE OF OPERATION
A mesh is made of fine wire with windows of size of approx. 9"*9". The interconnecting wires of the mesh are looped around the fence wires so that it is not possible to separate the mesh from the fence with out cutting it. The mesh is terminated to a Pick-up unit. The pick-up unit sends pulses at regular frequency through the wires of the mesh and monitors the return signal. If the mesh is tampered, it results in a change in the return signal which is detected and alarm is raised.

The core of the mesh wire is made of a Stainless Steel wire twisted with 4 leads of fine copper wire. Three of these wires are monitored at any point of time while the other two are kept as spare. It is almost impossible to remove the PVC sheathing and separate the twisted wire leads with out causing an alarm. Hence the intruder cannot bypass the system by clipping long leads of wire across two points of the mesh and cutting the mesh in between, as any action to remove even the insulation may itself trigger an alarm. An intruder may also try to stretch the mesh for gaining access through the stretched hole, instead of cutting the wire. But if he stretches the mesh to beyond 30 % of its original size, the copper wires break creating an alarm condition.

The mesh is made of interleaving wires and the intruder cannot detect the exact route. Hence he will create a wrong routing, which again is easily detected. Even if he is able to trace the route, and connect a by-pass lead, this will result in a change in the signal being monitored by the pickup unit as it is not possible to connect all the three monitored wires.

In a nutshell it is not possible at all to cut through the pulsed wire mesh without being detected.

System Components

1) Wire mesh.
The wire mesh is made of fine insulated wire. It can be made in the field to meet the exact nature of the fence being covered by the system. The wire is rated for withstanding extreme climatic conditions.
2)Pick-Up unit
Each Pick-Up unit can cover a maximum of 12 meters of a fence of height approx 2.6 meters. The unit is fixed to the fence post.
3) Field Unit
7 pick-up units covering a frontage of 84 meters form one detection zone. Each Field unit will control two detection zones ( 2 X 7 pick up units) with a total frontage of 168 meters.
4) Local Alarm Unit
Each Field unit is connected to one Local alarm unit, which is placed in the sentry post. The Local alarm unit gives audio visual zone wise alarm indication.
5) Battery Power Pack
The battery power pack provides 12 V, Dc power for the system. It has a built in charger which charges the battery from AC supply input ( 100 V AC – 300 V AC). When mains power is available the system is powered by the mains power and the battery gets charged. When the mains power is not available, the battery feeds the power to the system via the auto changeover circuit. The Local alarm unit also gives alarm indications for ‘Low Bty’, Communication failure. The power pack is supplied with 12 V, DC 92 AH, maint. Free fully sealed bty.

Scope of Supply per KM of frontage
1) PWM wire mesh of height 2.6 mtrs : 1 KM length in modules of 3 mtrs.
2) Field units :                                        6 Nos
3) Alarm Units :                                      6 Nos
4) Battery Power Pack :                        3 Nos
5) Armoured data cable :                      Approx. 600 mtrs

Comprehensive fence protection
A fence can be violated by one of the following means.
1) Cutting through the fence
2) Crawling underneath / burrowing under the fence
3) Jumping over the fence.
No single system can provide protection against all these three modes of intrusion. The most common method is cutting through the fence and the PWM provides the most reliable protection against this.

The same mesh can also be installed to cover the gaps under the fence and if required under the ground also to protect against intruders crawling underneath the fence by digging.

Jumping over the fence has two possibilities. The intruder can rest a ladder on the fence overhang and climb over it or. In this case an optic fiber mesh may be able to detect as it can sense the change in the pressure on the fiber wires. But the same advantage becomes a disadvantage as heavy birds sitting or taking off from the fence, falling snow or heavy down pour may generate false alarms. The intruder can alternatively use a self-supporting ladder and jump clearly over the fence. Even the optic fiber mesh cannot detect this. The PWM system is a better alternative to the Fiber Optic Mesh and available at less than 1/3rd of the cost of the Fiber Optic Mesh.

If climbing the fence also needs to be deterred, a separate system can be provided for this to provide comprehensive protection. Electric fence wires can be installed as a overhang to the existing fence to prevent climbing over the fence.

Protection against animals
The PWM system detects only breach or Cut through attempts. The same PW mesh can also be cut by animals moving near the fence and trying to get access by braking the fence wires. This will also raise alarm as the system is designed for detecting cut in the wires. Hence, as in the case of Fiber Optic Mesh, suitable protection has to be undertaken. One way is install protective GI wire mesh on the PW mesh. Even placing concertina coils or spikes in front of the fence may
prevent the approach of animals near the fence and greatly reduce the chance of damage to the PW Mesh.