These are one of the most used intrusion sensors and can usually be found on doors and windows. They consist of a detecting magnet also known as a switch, generally attached on the fixed part of the opening, and a magnet, installed on the mobile part. These two components generate a magnetic field around them that is interrupted when the entry point is opened. In that situation, the detecting magnet detects the difference and alerts about the opening. Magnetic switches can be used on other applications like closets or to secure objects in a fix position. Additionally, it is worth knowing that some of these intrusion sensors come with balanced switches (Balanced Magnetic Switches) that create a secondary magnetic field to help to prevent defeat.

Generally installed on walls or ceilings, these sensors are used to detect when a glass is broken. When glass breaks, it emits soundwaves at a specific frequency that is recognised by the sensor, generating in this way an alert. The disadvantage of acoustic sensors relies on the possibility of experimenting false alarms when, for instance, you break a cup, shake some keys or operate some machinery.

These shock sensors detect the movement of the surface to which they are secured. They are generally attached on doors, glasses and walls, but it is essential to know that not all vibration sensors may be able to detect the movement on all types of surfaces. This is because each surface has its' own structure and consequently, they vibrate at different frequencies. One of the main advantages of vibration sensors is that they can detect break-in attempts before they happen. On the other side, although they are designed to ignore normal building vibrations, on some occasions, they can be the source of false alerts.

These sensors are generally used in entry points like garages, doors and gates. They consist of a transmitter that emits a beam of infrared light to a receiver. When the beam is interrupted by any object, an alert is generated. For security purposes, the beam can be made invisible, and if needed, a series of transmitters and receivers can be combined to increase the number of beams and with this extend the area covered.

The application of capacitance sensors is limited to metal objects like safes or file cabinets, and they work using the same principle of capacitors. The metallic objects to be protected present insulation feet that separate them from an electrical ground plate. This separation creates an electrical charge that will change value when the protected object is approached or touched by someone, creating, in turn, an alert.

These are motion detectors used to protect either rooms or corridors. They measure energy radiated by objects and thermal energy changes on the background of a scene is covered. On one side, this means that when a new source of energy, like a human, enters a space covered by the sensor, an alert is sent. Some sensors allow distinguishing between adults, child and pets. On the other, if a source of energy that was already present in the initial scene moves and covers the energy emitted by the objects in the background, an alert is also sent. Depending on the lenses of the passive infrared sensors, these will be suitable for covering short or long distances and wide or narrow field of views.

These sensors measure the variances between the emitted and received signal caused by the movement of any object within the energy field created. Because of their operating principle, they better detect motion that is either close or away from the sensor. One of the advantages and disadvantages of this type of sensors is that they can penetrate walls going outside of the desired area. While concrete might not be traversed and metal objects can cause irregular coverage, most plastics, glasses and other materials are penetrated.

These sensors detect the weight of a person or object when these pass over them. They usually present the shape of a mat but can also be placed under other objects.

There are some solutions in the market that combine more than one technology in a single sensor. The most common combinations are passive infrared and microwave sensors, or passive infrared and acoustic sensors.