Burglary: How perpetrator behaviour is changing

Glass break detectors - proven technology with a new significance

Just 10 years ago, glass breakage detectors were part of the standard repertoire of any security concept.

"However, the media coverage of burglaries and thefts has led to the impression that windows, for example, "no longer break glass", that perpetrators can only get in by levering open the window mechanism. However, the statistics do not bear this out. Perpetrator behaviour is now much broader, so we have to adapt accordingly when creating security concepts. History shows that there is a perpetual arms race between perpetrators and security systems," says Sascha Puppel, publicly appointed and sworn expert for security technology and security concepts and board member of the Bundesverband Sicherheitstechnik e.V. (BHE).

"Mechanical security systems that are sensibly coordinated with each other are the first line of defence against burglary and form the basis for a solid security concept."[1] Electronic security systems offer additional protection. This approach and the experience that perpetrators were often able to break in by prising open in the past has now led to (display) windows and patio doors being converted and retrofitted. This includes, for example, retrofitting mushroom-head pins, lockable window handles or screw-on security devices that make unwanted entry more difficult.

Prying open with a screwdriver is still the most common method for the opportunist thief[2], who in most cases "seizes the moment". However, this method is now closely followed by piercing the glass seal. Burglars pierce this with a screwdriver in order to reach the window handle or patio door handle. If they can move it, the window or patio door can be opened very easily[3].

In order to achieve effective protection against this now common method, additional electronic protection of the window or glass surfaces is advisable. This can be achieved, for example, by professionally installing a glass breakage detector. Glass breakage detectors are electronic sensors which, when connected to a burglar alarm system, provide early warning of danger. There are different types of glass breakage detectors, including active, passive and acoustic models, each of which has its own advantages, disadvantages and areas of application.

Active glass breakage detector

Active glass break detectors transmit ultrasonic signals via the glass. In the normal state, this transmission behaviour is evaluated and any changes that occur when the glass breaks trigger an alarm.

Active glass breakage detectors are suitable for all glass surfaces, especially for laminated glass or glass covered with film, on which passive and acoustic glass breakage detectors do not work from a purely physical point of view. They enable precise detection of glass breakage, even with different glass thicknesses. Active glass breakage detectors are also the only option for glass monitoring in accordance with VdS Class C.

Passive glass breakage detector

In contrast, passive glass breakage detectors do not use emitted signals, but react to the sound waves that are generated when glass is broken. The detectors are equipped with sensors that react not only to the characteristic frequencies of glass breakage noises, but also to the amplitude. As soon as these are detected, the detector triggers an alarm.

Passive glass breakage detectors are suitable for single-pane glass such as float or toughened safety glass. They are basically easy to install, but special attention must be paid to the bonding point. Unlike active glass breakage detectors, passive glass breakage detectors cannot detect if the detector becomes detached from the glass or if there is a defect in the actual sensor element.

Acoustic glass breakage detector

Acoustic glass breakage detectors use microphones to detect the sound waves of glass breakage. These microphones are programmed to identify the characteristic sounds of breaking glass and trigger the alarm.

Acoustic glass breakage detectors are particularly suitable for doors and windows with several panes of glass next to each other. They always require a short distance to the glass and a direct "line of sight". "However, many sound-absorbing materials in the room, such as a thick carpet or curtains, can lead to reduced detection reliability. To ensure optimum functionality, the placement and number of detectors must be taken into account accordingly," says Puppel.


Integrated into a holistic security architecture and a security concept that takes into account mechanical and electronic technology as well as security-conscious behaviour (organisational and personnel measures including intervention), glass breakage detectors are an important component as a proactive measure. The active glass breakage detector, which even monitors its own function and has a special VdS-C class certification, provides the highest possible level of security for subsequent glass monitoring. The high level of reliability and early alerting make glass breakage detectors an indispensable element in minimising risk and protecting people, assets and sensitive information.

[1] https://www.polizei-beratung.de/themen-und-tipps/einbruch/technische-sicherheit/

[2] https://www.kriminalpraevention.de/files/DFK/dfk-publikationen/2004_wirksamkeit_kurzfassung.pdf Even though the police and insurance companies confirm that burglaries are always planned, it is often the arrival of favourable opportunities that triggers the choice of a particular property.

[3] https://www.zuhause-sicher.de/einbruchschutz/einbrueche-wissenswertes/taeter-arbeitsweisen/

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