Intrusion alarm system

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Burglar alarm systems ( EMA ) are technical, nowadays exclusively electronically operated devices that serve to protect property and people . A burglar alarm system should

Working principle and types

Today alarm systems are divided into three main technical categories:

Direct current
DC technology
Here an electrical current flows between two points within the alarm system, the zone , via a detector. In the center of the burglar alarm system or raid alarm system (I & HAS) is based on the principle of a Wheatstone measuring bridge by means of a differential loop the voltage measured and compared with a target value are compared. A resistor inside the detector or in the junction box furthest away from the line forms one of the four resistances of the measuring bridge. If the voltage falls below or exceeds a certain threshold value , this is evaluated as an alarm or sabotage . In addition to zones for burglary or hold-up, there can be additional zones for sabotage detection, which are monitored according to the same principle. All opening contacts of detectors, distributors, etc. are looped into this zone. The interconnection of the resistors and the triggering criteria depend on the manufacturer of the EMA / ÜMA and the specifications of the VdS.
Bus technology
In the bus technology z. B. all detectors are connected via two pairs of wires, one pair of wires being the data line and the other being used to power the alarms and other end devices. If there is a common ground, three wires are sufficient. There are also bus systems that work in conformity with VdS ​​with only two wires. This technology makes it possible to connect a large number of detectors to a thin cable. The EMA / ÜMA is usually configured using a PC that is connected via a serial or parallel interface. Each detector is assigned an ID , the bus address, and, if necessary, a text or a definition of the detector. The system now queries the status of the alarming units via the data line in regular cycles .
Radio technology
EMA / ÜMA that work with radio technology work like bus systems, except that the cabling is replaced by radio. VdS-compliant systems work in the 433 MHz or 868 MHz range. The detectors have a battery, which must ensure the power supply for at least one year.

If an alarm occurs, different reactions are carried out for all technologies depending on the requirements and programming . B. dialing devices, alarm transmission devices, signaling devices, cameras, etc., can be controlled or triggered.

There are also two categories of purpose:

An open hazard alarm center with IP / ISDN transmission unit and the option to operate detectors in direct current, bus and radio technology.
Burglar alarm systems (EMA)
are used to detect and report intrusions
Assault alarm systems (ÜMA)
are used to manually trigger a hold-up alarm by people during or after a hold-up.

Most modern intrusion alarm centers (EMZ) also support the functions of an ÜMA, so that EMA and ÜMA can be combined without any problems. Is hereby requested that the attack detector can be turned on its own detector group and configured. A hold-up alarm group is always in operation, even when the intrusion alarm system is disarmed. Intrusion alarm groups are only armed when leaving the premises. In order to avoid false alarms , there is the principle of inevitability in Germany . The inevitability of arming ensures that arming can only take place when all detectors are in the correct state (idle state). The inevitability of disarming ensures that the monitored rooms can only be entered after the arming has been canceled (disarming). In all systems, the control centers are equipped with accumulators, which, depending on the classification of the property, must ensure the power supply for at least 12, 30 or 60 hours if the 230 volt network fails.

Security levels

In principle, a distinction is made between four different levels of security for intrusion alarm systems. With an increase in the level of security, the security against overcoming also increases. Since a grade 1 alarm system does not fully meet the requirements recommended by the police, devices of this classification are not recommended. Grade 2 EMAs are intended for apartments and houses, but are recognized by most insurers for commercial properties without any particular risk. Grade 3 EMAs are designed for residential buildings with an increased risk potential as well as for commercial and government properties. Grade 4 EMAs are intended for buildings with a very high risk potential. These offer the highest level of overcoming security and responsiveness.

Alarm indicator

Alarm indicators are used to trigger an alarm and are divided into two main groups:

  • Non-automatic detectors
    • Assault detectors (cash registers, VS , weapons rooms)
    • Money contacts (cash registers)
    • Hold-up bars (cash registers)
    • Striking plate contacts (doors)
    • Print carpet (entrance areas)
    • Pull wire (doors)

Most detectors can also be assigned to a monitoring type:

  • Outer skin monitoring: Here special emphasis is placed on the detection of an intrusion from the outside into the object (windows, doors, walls, floor)
  • Trap surveillance: This type of surveillance is intended to detect an intruder inside the property, e.g. B. with the help of motion detectors
  • Focus-based monitoring: Particularly endangered areas or objects are specifically monitored, e.g. B. Safes and works of art.


  • Signal transmitter: Depending on the type of object to be monitored, optical or acoustic signal transmitters are used to signal a break-in or hold-up.
  • Dialing device: In most cases, it is desirable or even required to transmit an emergency incident to the emergency services immediately. This is done either via a dedicated line directly to the police (with the help of a so-called main reporter), via the telephone network ( analog or digital ) to a security service or a security center commissioned with it, or via the GSM network . Dialers can be programmed to notify different or multiple locations in different situations or at different times. Either recorded voice messages or digitized information (similar to fax machines) can be transmitted. Newer technologies use the virtual dedicated line X31 to ensure constant monitoring of the telephone line and to secure the redundant transmission path.
  • Video memory: Video memory records video films or individual images at the moment of the alarm. Depending on the type and configuration, a certain period of time is saved before and after the alarm in order to facilitate reconstruction and identification of the perpetrator . There are analog (analog camera and video equipment) and digital (digital or analog camera in connection with a computer) video memory.
  • Photo camera: Photo cameras produce photos at regular intervals over a certain period of time. The first photo is taken when the alarm is triggered, even if this technology has been largely replaced by video memories, there are still numerous banks today in which photo cameras (mostly black and white ) are used.
  • Event printer : This printer records all events in order to determine the origin of an alarm and to be able to reconstruct the situation . Modern alarm systems automatically fulfill this function with an internal memory and a display, but a printer can make the task easier and also enables problem-free and inexpensive portability of the data .


According to DIN VDE 0833-3, alarms from EMA and / or ÜMA are generally sent via an alarm receiving center (AES) certified according to DIN EN 50518 (VDE 0830-5-6 ) to a DIN VDE V 0827-11 (VDE V 0827-11) to connect a certified emergency call and service control center (NSL). Alternatively, a connection to the police can take place in accordance with the police ÜEA guideline .

A distinction is made between silent alarms, acoustic alarms and visual alarms as well as internal alarms, external alarms and remote alarms


In order for an intrusion alarm system to trigger an alarm when a break-in is detected, it must be "armed". On the other hand, an authorized person must be able to deactivate the system in order not to trigger the alarm. Various technologies can be used for this, which are used depending on the situation and manufacturer. Their combination is also often useful.

On the one hand, systems are available that require a physical key for arming. These can be mechanical key switches, which are usually equipped with a pin or a Chubb lock. Electronic keys with an integrated processor that enable contactless authorization via RFID or physical contact are also possible. These electronic keys can be in the form of small key fobs , chip cards or combined with a mechanical key. Also magnetic cards are used, but may pose a security risk.

On the other hand, systems are used that either require the entry of an access code / password or check a biometric feature, e.g. B. the fingerprint or the iris .

The activation unit must always be structurally outside the secured area in VdS-compliant systems and in accordance with the activation conditions of the police. The system can only be armed when all door contacts are closed, motion detectors do not register any movements and all other alarm transmitters do not detect anything.

In the case of systems that do not trigger a direct notification to the police, the stipulations of DIN EN 50131 often refrain from spatial separation for reasons of cost. Arming takes place shortly before leaving the secured area, usually directly on the control unit, and disarming shortly after entering the area. Since insurance companies mostly recognize systems installed in accordance with DIN EN 50131 in the private and commercial sector, it is considered sufficient in many cases.

Of the so-called late Heimkehrer circuit ( engl. Late return disarming feature , also internal sharp-external focus circuit , ISEU circuit or tippler circuit ) occurs when the system is activated from the inside and can be deactivated from the outside.


Contrary to the general film scene, modern alarm systems are very well secured against sabotage . The only way to sabotage an alarm system is to manipulate it while it is unset. However, even this is evaluated by standard alarm systems as an attempt at sabotage, which triggers an alarm, and serious attempts at manipulation can only be carried out by the installation circuit, for which both the code of the installation company and an authorized user are required.This manipulation can only be performed under sight and thus take place with any witnesses present - in the case of the installation circuit even only with the cooperation of the person responsible for the system. It can be demonstrated in detail later . Here are a few obvious ways sabotage can be used and how to prevent them:

  • Separation of a detector: In the case of detector groups using direct current technology, a known current flows permanently. A change in this current caused by manipulation of the line triggers an alarm. In systems with bus technology, the central control unit detects a missing element and triggers an alarm.
  • Bypassing a detector: There is a defined resistor at the end of each DC drum group . If this is bridged, z. B. by a previously manipulated alarm device or with a wire, the measured resistance value changes, which is recognized by the control center and evaluated as a (sabotage) alarm.
  • Cover of a motion detector: Modern IR motion detectors have visual recognition. Are they sprayed with paint or with a cardboard box or something similar? covered, the changed "visibility" is recognized and reported as a sabotage alarm (regulation for devices of class VdS-C).
  • Manipulation of the periphery inside: In theory, it would be possible to manipulate the trigger contact of a detector. Modern and older elements, however, have a so-called cover contact that is assigned to the same detector group as the alarm contact (not VdS-compliant) or is connected to a separate sabotage line (VdS-compliant). If the housing is opened when a sabotage line is connected, an alarm is triggered even in the unset state ("sabotage").
  • Interrupting the dedicated line: Since special systems (e.g. buildings with high material values ​​such as a museum) have a main alarm that reports an alarm to the responsible police via a dedicated line, it sounds tempting to cut the dedicated line. The problem, however, is that the dispatcher has to continuously transmit a signal to the police reception center. If this signal is not received, the receiving device reports an immediate alarm. In addition to the signal, the dedicated line is also monitored by a resistor on the part of the receiver, which prevents bridging.
  • Disconnection of the telephone line: This would prevent the dialer from making an alarm call. However, this must transmit a status report to a recipient at regular intervals that are unknown to a potential perpetrator. If the so-called routine call is not made, appropriate measures are initiated depending on the property and guidelines. DIN EN 50131 recommends or requires under certain circumstances that two independent transmission paths (e.g. telephone network / VoIP and mobile radio) are available. This means that alarm messages can also be transmitted after a transmission path has been sabotaged.

Regulations and guidelines

In order to guarantee the safety of objects and people, various national and international bodies issue regulations and guidelines with regard to alarm systems. This includes the police or, in Germany, VdS Schadenverhütung GmbH.

The following must be observed in particular during planning, configuration, installation and maintenance:

  • DIN EN 50131-1; VDE 0830-2-1: 2010-02 Alarm systems - intrusion and hold-up alarm systems
  • DIN VDE 0833-1 Hazard alarm systems for fire, burglary and hold-up - Part 1: General specifications
  • DIN VDE 0833-3 Hazard alarm systems for fire, burglary and hold-up - Part 3: Specifications for intrusion and hold-up alarm systems
  • VdS 2311 intruder alarm systems, planning and installation
  • ÜEA guideline for systems connected to the police

These standards and guidelines specify, among other things, the type, positioning and number of alarm indicators, the type of alarm transmission and signaling, protection against sabotage and the maintenance periods for functional testing.

Alarm systems and the European installation bus (EIB)

VdS -certified alarm systems cannot be set up with the EIB , although most of the EIB alarm systems are strictly based on VdS. The market also offers alarm systems with an EIB interface. For a VdS certification, the EIB interface may only be used as an output, ie only the status information of the alarm system is forwarded to the EIB.

See also


  • Hans-Joachim Geist: The successful installation of a burglar alarm system , Elektor-Verlag 1999, ISBN 3895760803
  • Adam Merschbacher : Security analysis for households , VdS-Verlag 2002, ISBN 3936050031
  • Gilles Vernet: alarm systems. Conception and construction with commercially available components , Elektor-Verlag 2002, ISBN 3895760137
  • Bodo Wollny: Alarm Systems , Pflaum 2003, ISBN 3790507776
  • Hans-Joachim Geist: ALARM in the event of a break-in. Via cable, radio and satellite , Elektor-Verlag 2003, ISBN 3895761338
  • Hans-Werner Bastian: Security check for house and apartment. Protection against burglary, fire and water damage , Eccomedia 2003, ISBN 393678213X
  • Adam Merschbacher: Safety analysis for commercial enterprises , VdS-Verlag 2003, ISBN 393605004X
  • Bodo Wollny: Alarm systems. Planning, components, installation. , Pflaum 2003, ISBN 3790509035
  • Jascha Schmitz: Your safe house - the guide to alarm systems, fire protection and access security, free e-book (38 pages)

Individual evidence

  1. Police crime prevention program
  2. DIN VDE 0833-1: Hazard alarm systems for fire, burglary and hold-up - Part 1: General specifications . September 2009.
  3. Langenscheidt technical dictionary technology and applied sciences: English - German / German - English, entry late return disarming feature . Digitizedhttp: //vorlage_digitalisat.test/ double-sided%3D~ LT% 3D ~ PUR% 3D
  4. DIN EN 50131-1; VDE 0830-2-1: 2010-02: 2010-02., accessed on February 20, 2012 .
  5. VdS Schadenverhütung (publisher): VdS guidelines for burglar alarm systems; planning and installation .