How the burglar alarm and detectors are arranged and working

Issues of home security and property conservation concern every apartment owner. People solve them in various ways, including the installation of a security alarm, which allows to effectively identify the occurrence of an unusual situation in their area of ​​residence, and take effective measures to prevent theft.

The term security alarm refers to a set of technical means operating in automatic mode, which is designed to detect cases of unauthorized access of people to the protected zone and take effective measures to suppress them.

The principle of operation of the security alarm

Typically, the controlled space is divided into several composite zones, including:

1. external lines of observation of the approach to the house;

2. the interior space of the apartment;

3. the condition of the fencing of building structures with the ability to penetrate through: walls, windows and doors, roof, basement.

The simplified structure of such a system can be represented as:

• protected area surveillance systems;

• a logical unit that processes and transmits incoming information;

• warning devices;

• channels and means of communication.

The relationship of the elements shown in the picture.

Security Zone Monitoring System

The sensitive element of the system is detector detector, which can track the intrusion into the territory of the admission according to different principles, for example:

• rupture of an electric circuit upon breaking an inconspicuous thin wire hidden in the grass near the house or pasted with a thin ribbon of foil over the surface of a glass or wall;

• microswitch trips when opening a door or under the weight of an attacker’s body on a controlled site;

• movement of the magnet relative to the reed relay;

• glass impact and many other factors.

According to the principles of operation, the detector is:

• electrocontact;

• magnetic contact;

• shock contact;

• piezoelectric;

• capacitive;

• optoelectrical;

• sound;

• ultrasonic;

• combined and other types.

According to the type of controlled zone, the detectors are divided into:

• voluminous;

• superficial;

• linear

• point.

Magnetic Contact Detectors

Magnetic sensors (locks) are mounted above the doors and windows. They consist of Reed relay kit with magnet and are triggered by manipulations to open or close the leaf of the sash.

The disadvantage of this type of sensor is the ability to hold it off from the energy of the field of an external powerful magnet that attackers can use.

Glass Break Detectors

Glass surfaces occupy a large plane on building structures and are easily broken. Through the openings made, it is not difficult for attackers to enter the protected area.

Glass breaking sensors create according to different principles of operation, which criminals use due to:

• striking;

• extrusions;

• heating up.

Initially, such sensors are mounted directly on the glass. They respond to acoustic or mechanical vibrations of a controlled surface.

Shock-contact and piezoelectric detectors act on mechanical vibrations.

Contact sensors monitor the integrity of the glass surface on which they are glued.

Passive sound detectors operate on low-frequency sound produced by hitting glass and high-frequency acoustic signals from flying fragments. They compare the sequence of recorded oscillations and, when it corresponds to breaking the glass, give a signal about the operation.

Infrared detectors

They are created according to various principles: passive and active.

Passive detectors

Sensors of this type monitor a certain area by the amount of heat in the protection zone. The temperature created by the appearing human body is well felt by the receiving device and leads to the operation of the system.

In order for criminals to be able to overcome the response zone of a passive infrared detector, they need to put on a suit that completely blocks the radiation of the body’s heat fluxes into the environment. Such capabilities are possessed, for example, by the full equipment of a fire rescuer.

Active Type Detectors

The composition of such a sensor includes an infrared active transmitter and receiver. They work as a kit. Invisible to the human eye, a beam of radiation is constantly sent from the transmitter to the receiver. If it is blocked, then an alarm immediately occurs.

Criminals can get around this beam by crawling from below or stepping over it. But, for this they need to know his whereabouts.

Radio wave sensors

They work on the principle of emitting radio waves into the room and receiving reflected signals from all objects. When the situation in the room does not change, a static balance is created. If the movement begins, for example, by a walking person, then the total comparison of the waves begins to change, which leads to a sensor.

The disadvantage of this design is that an attacker can move very slowly in a controlled area and this will allow him to prevent the possibility of an alarm.

Capacitive Sensors

Instruments of this type have a capacitive charge balanced with the surrounding space. They register a change in the energy of the electric field located near them. When a person approaches the detector, the capacity of the charged capacitor decreases due to the draining of part of the charge on the body and an alarm occurs.

A criminal can prevent the capacitive sensor from working if it blocks the drainage path of the capacitor discharge current from itself. To achieve this, it is enough to use electrical protective equipment used by electricians working on equipment that is under high voltage: dielectric gloves, helmet and electrician's suit.

Combined Detectors

In their design, they combine the functions of infrared passive sensors that respond to human thermal energy and radio wave models that take into account the movement of people in a controlled space due to distortion of the structure of electromagnetic waves.

Combined sensors for criminals are quite difficult to fool because of their high sensitivity and at the same time taking into account several triggering factors.

The design of sensitive elements that respond to the penetration of unauthorized persons is constantly being improved. Popular among the population are motion sensors and video surveillance systems.

About the video surveillance system on video (selection, installation, budget solutions):

When using any type of sensors, it should be borne in mind that they are technical means that perform only certain functions. They can be blocked by various methods.

Therefore, having established an individual alarm system, it is necessary to mask its sensors and blocks as much as possible, to limit the access of any surrounding persons to the security circuit. The fewer people will know the specific characteristics of your equipment, the more difficult it will be for attackers to crack it.

Unauthorized entry alert scheme

If the detector detector has the function of detecting a violation, then the siren has other tasks:

1. scare off a potential criminal by the sound of a siren or a light signal;

2. Either promptly inform the owner of the property about an attack on his property or secretly call the security representatives or the police brigade to detain the offender.

To solve the second problem, not wired, but mobile means of transmitting information using the principles of cellular communication and Internet channels are becoming increasingly popular.

The principle of operation of logic devices

Depending on the principles of building a control system for the security zone, warning schemes for the owner of the premises and security services, various designs of reception and control units are created. They process the information coming from the surveillance systems, detect the moment of violation of the security boundaries and issue a command to trigger sirens.

Among them, factory security devices with a controller programmable for local conditions are in demand.

Channels of connection

Information between internal alarm devices is transmitted by:

1. wires;

2. radio channels.

To implement the second method, it is necessary on each block to have an autonomous power source.

Continuation of the article:Security Alarm System