1 INTRUSION ALARM TECHNOLOGY DETECTION DEVICES. 2 INTRUSION ALARM TECHNOLOGY Detection devices can be either passive or active. Passive devices typically

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INTRUSION ALARM TECHNOLOGY

DETECTION DEVICES

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Detection devices can be either passive or active.

Passive devices typically only require two wires and don’t require power.

Active devices typically require 4 wires, two wires are for power, the other two are for the detection loop.

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In this presentation we will cover the most commonly used detection devices for intrusion detection systems.

One of the most commonly used detection devices is the magnetic switch sensor.

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The magnet controls an arm in the switch, when the magnet is removed the metal contact if it is a normally closed switch will make contact and open the circuit.

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The magnetic switch sensor is used to protect the perimeter of a building and is typically used on doors and windows.

There are three different magnetic switch technologies;

1) Magnetic mechanical switch

2) Magnetic reed switch3) Balanced magnetic reed

switch

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The magnetic mechanical switch consists of a magnetically actuated switch and a magnet.

These switches can handle relatively high levels of current and are vibration sensitive.

They can be either N.O. or N.C. and require a relatively high current to operate.

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The magnetic reed switch is an electrical switch operated by an applied magnetic field.

It contains two ferrous magnetized strips that react to a permanent magnet and have a long operating life.

They can be either N.O. or N.C. or both depending on how it is wired.

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The balanced magnetic switch uses a balanced magnetic field, any change in the magnetic field trips an alarm.

These types of switches are hard to circumvent and are also vibration sensitive, they also operate on a relatively small current.

They can also be wired as either a N.O. or N.C. device.

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22/2 or 22/4 would be the best choice of cabling for these devices.

The surface mount magnetic switch comes with additional parts; a cover that conceals the screw terminals and spacers to properly align the magnet with the sensor.

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Contrary to Hollywood movies and shows a piece of aluminum foil from a stick of gum placed between the contact and magnet will not defeat the loop, I encourage you to try it when you install a security system in lab.

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Magnetic switch contacts are also available as flush mount type contacts, they’re normally used for doors, the magnet goes into the door and the switch is placed in the door frame.

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When placing a door contact, surface mount or flush mount it should be installed approximately 4” from the opening side of the door.

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Glass break detectors detect the frequency of breaking glass.

Glass break detectors are designed for specific ranges of glass, not all glass is constructed the same.

Metal oxide coatings, safety glass and tinting can dramatically reduce the frequency of breaking glass so care has to taken when choosing these types of detectors.

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The type of glass can found by locating the installers mark in the corner of the glass pane.

Glass break detectors are designed to be mounted directly on the window, some are designed to be placed in the vicinity of windows. THIS GLASS

DETECTOR IS DESIGNED TO BE PLACED WITHIN 30’ OF THE WINDOWS

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Glass break detectors can be standard detectors, dual frequency detectors or three frequency detectors.

Standard detectors monitor the high frequencies of breaking glass.

Dual detectors monitor the low and high frequencies.

Three frequency detectors monitor low, mid and high frequencies of glass breaking

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Glass break detectors are sometimes called acoustic sensors, sensitivity of these detectors needs to be increased to compensate for heavy drapes or fabric style venetian blinds.

These are active devices that require power, the next slide shows how to properly wire an acoustic detector.

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Wiring a glass break detector;

THIS DEVICE IS POLARITY SENSITIVE

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Glass break detectors should always be tested with a glass break simulator.

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PIRs (passive infrared) detectors are very common and used in almost every security system.

These devices also require power and polarity needs to be maintained when wiring them.

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PIRs are used for interior protection and perceive and respond to a change in infrared energy, a form of heat.

All objects above absolute zero emit heat energy in the form of infrared radiation (infrared light). Usually infrared light is invisible to the human eye, but it can be detected by electronic devices designed for such a purpose.

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PIRs offer a number of different coverage patterns;

1. Short range 25’2. Medium range 50’3. Long range 100+’4. Wide angle5. Narrow angle6. Pet alley

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Dual technology PIRs use both infrared and microwave technology to sense movement, both sensors must be tripped to activate an alarm.

The dual technology sensors are designed to eliminate or reduce false alarms.

PIRs should not face windows, heating systems or air movement from central air ducts.

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Wiring a PIR sensor;

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Some PIRs have a different type of dual technology, they come equipped with cameras.

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They are many different types of detectors out there, but the ones we just covered are by far the most widely used.

Pressure mats are another option for perimeter protection and photo electric beams are fairly popular too, especially with small shops.

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1 INTRUSION ALARM TECHNOLOGY DETECTION DEVICES. 2 INTRUSION ALARM TECHNOLOGY Detection devices can be either passive or active. Passive devices typically