Anti-masking and its implementation in Ajax outdoor detectors


To gain entry into an object protected by an outdoor alarm system unnoticed, intruders sabotage motion detectors in the first place. As soon as the security system is disarmed, they penetrate the territory and block the view of motion detectors, i.e. mask them.

To protect the security system from this type of sabotage, outdoor detectors are equipped with anti-masking systems. The most advanced anti-masking systems respond to all typical tricks: placing obstacles in front of the sensors, painting the body or covering it with a cloth, or even varnishing the detector.

Indoor motion detectors feature anti-masking systems on rare occasions. They are used in parallel with other types of detectors (e.g., window opening or glass breaking detectors), therefore if sabotaged, they do not allow for invisible penetration.

Anti-masking system in Ajax detectors

The anti-masking protection system of MotionProtect Outdoor detector includes three infrared sensors and a special software algorithm.

ajax antimasking

MotionProtect Outdoor is protected from all cases of masking:

  • when an obstacle is placed in front of one or both detector lenses
  • when one or both detector lenses are painted over or something is stuck over them
  • when the detector body is coated with transparent varnish (usually urethane)

Intruders may use a transparent urethane varnish to mask motion detectors with PIR sensors. It blocks infrared radiation, and the detector stops reacting to motion. The device looks normal and does not attract attention, unlike when it is covered with a cloth or painted over.

And to ensure maximum protection for masking sensors of the outdoor detector from rain and snow, a special visor was developed additionally — Hood for MotionProtect Outdoor.

It takes 1 second to 5 minutes to detect a masking attempt of MotionProtect Outdoor, depending on the security mode and the type of masking.

With the Anti-masking option enabled, the detector reacts to masking regardless of whether the security system is armed or not.

As soon as a threat is identified, the detector lights up the green LED for 1 second and sends notifications to all users and to the security company.

The MotionProtect Outdoor anti-masking system conforms to Grade 3 integrity level of security standard EN 50131. This means that the system is ready to confront intruders with professional skills and knowledge.