This article is a quick reference for everyone who considers getting an Ajax Systems’ sensors, and a title reflects content with a 100% accuracy – 20 Ajax Systems’ Sensors in 1 article with a tips, tricks, descriptions, advises for every single 1 of them, and altogether about Ajax Systems sensors, what are they intended for, why do you need them and et cetera.
The Review Includes
We are dividing the sensors into groups by their use purposes and features. Here they are below:
System’s Core:
Indoor Detectors:
Outdoor Section:
Fire and Leaks Prevention:
Control Devices:
Sirens and Buzzers:
Ajax Brains
Part 1, the Ajax Brains:
- Ajax Hub
- Ajax Hub Plus
- Ajax Rex
Ajax Hub: The Core of the System
Your journey with Ajax Systems starts with the Ajax Hub - this is the brain of the system.
A quick introduction: None of the sensors connect to the internet directly. Each sensor has only one communication channel - radio waves using the Ajax Jeweller radio protocol, which operates on 868 MHz frequencies.
That brings us to the role of the Ajax Hub: it acts as a bridge between the sensors and the user. The Hub converts signals received from sensors into actionable notifications, which are then sent to your smartphone via the internet. The Hub manages the entire data exchange process, monitors sensor status in real time, and determines how to respond to incoming signals.
Hub Versions: Hub, Hub 2, Hub Plus
The Hub 2 and Hub Plus are extended versions of the basic Hub, featuring several improvements, primarily increased system capacity:
Hub and Hub 2 support up to 100 devices, up to 50 users, 50 rooms, and 9 user groups.
Hub Plus expands this to 150 devices, 100 users, 50 rooms, and 25 user groups.
Another key difference:
Hub Plus includes Wi-Fi support and two 3G SIM slots, offering a total of four communication channels (Wi-Fi, Ethernet, and two SIM cards).
Hub and Hub 2 do not support Wi-Fi or 3G. Hub supports a single 2G SIM slot, while Hub 2 includes two 2G SIM slots.
In terms of performance, all Hubs share identical core specifications:
2,000 meters operating range
15 ms threat signal transmission time
12–300 seconds detector polling interval
Built-in lithium battery supporting up to 15 hours of backup power.
Camera & NVR Support
Since Ajax introduced third-party NVR and camera support, these numbers have also evolved:
Hub and Hub Plus support up to 25 third-party devices.
Hub 2 supports up to 50 third-party devices.
It's also important to note that Hub 2 is the only model currently compatible with the Ajax MotionCam sensor, as its name suggests.
Ajax Rex: Extending the Range
Now, let’s talk about Ajax Rex.
At first glance, Ajax Rex looks identical to the Hub - and that’s no coincidence. Essentially, Ajax took the Hub’s body, removed some of the “brains,” and added an extended battery. As a result, Rex can operate up to 35 hours on battery power, compared to 15 hours for the Hub.
But Rex’s purpose is very different: it is a radio signal range extender, not an internet signal extender. Rex creates an additional radio point within a range of 1,800 meters - just 200 meters less than the Hub’s own range.
It can support up to 149 connected sensors simultaneously.And here’s a clever feature: if Rex temporarily loses connection with the Hub, it is smart enough to maintain local communication with the connected devices until the link is restored.
Ajax Detectors Indoors
Part 2, Ajax Detectors Indoors:
- Ajax MotionProtect
- Ajax MotionProtect Plus
- Ajax CombiProtect
- Ajax MotionProtect Curtain
- Ajax DoorProtect
- Ajax DoorProtect Plus
- Ajax GlassProtect
Ajax Indoor Detectors
Let’s start with the fundamentals. The most basic alarm sensor type is the passive infrared sensor (PIR) - the core technology used in MotionProtect, MotionProtect Plus, and CombiProtect.
The working principle of a passive infrared sensor is simple: it detects changes in infrared radiation (heat) emitted by objects within its field of view. Since all warm-blooded creatures emit heat, the sensor identifies motion by detecting fluctuations in this heat signature. Both MotionProtect and MotionProtect Plus provide an effective detection range of up to 12 meters.
One key feature of MotionProtect is pet immunity: the sensor is designed to ignore movement from animals weighing up to 20 kilograms (44 pounds). This helps prevent false alarms in homes with pets.
MotionProtect vs. MotionProtect Plus
The difference between MotionProtect and MotionProtect Plus lies in the addition of a microwave sensor in the Plus version. This makes it more suitable for challenging environments such as rooms with air conditioning units, fireplaces, flickering lights, glares, or reflective surfaces.
However, this added capability comes at a small trade-off:
Battery life is reduced from up to 7 years (standard MotionProtect) to up to 5 years (MotionProtect Plus).
Communication range is also slightly lower - from 1,700 meters to 1,200 meters.
GlassProtect
Next is the GlassProtect - a small, compact sensor designed to detect glass breakage. It contains a built-in microphone and a sound level analyzer.
Its operation is based on two-step sound recognition to minimize false alarms:
It first detects the dull thud of an initial impact.
Then it listens for the specific sound of glass shattering and falling to the floor.
Detection range: up to 9 meters.Communication range: 1,000 meters.Alarm transmission time: 15 ms.Battery life: up to 7 years.
CombiProtect
Now, imagine combining the features of MotionProtect and GlassProtect in one device - that’s exactly what Ajax has done with CombiProtect.
CombiProtect integrates both an infrared motion sensor and a microphone for glass break detection in a single housing. This offers excellent versatility and cost-efficiency for protecting a wide range of indoor spaces.
Trade-offs to be aware of:
Glass detection range is slightly reduced to 3 to 5 meters.
Battery life is lowered to up to 5 years, which is expected given the dual-sensor functionality.
Communication range: 1,200 meters.
Summary
The Ajax Indoor Detectors line provides a versatile toolkit for comprehensive indoor protection:
MotionProtect: reliable motion detection with pet immunity.
MotionProtect Plus: advanced detection for complex environments with reflective interference.
GlassProtect: precise glass break detection with two-step sound recognition.
CombiProtect: an all-in-one solution combining motion and glass break detection, optimized for cost-effective setups.
These sensors offer flexible installation options and long-range, low-latency communication - all optimized to work seamlessly within the Ajax ecosystem.
Ajax DoorProtect and DoorProtect Plus
DoorProtect is one of the simplest yet most essential components of any Ajax security system. In essence, it is a reed switch sensor that detects whether a door or window is open or closed.
The operating principle is straightforward: it uses a reed switch and magnet combination. When the magnetic field is present (door or window closed), the reed switch circuit is closed (state "1"). When the field is broken (door or window open), the circuit opens (state "0").This simple mechanism allows for highly reliable perimeter protection.
The package includes two extra magnetic panels, designed to simplify installation on various surfaces such as doors and windows.
DoorProtect Plus
While the basic DoorProtect covers open/close status detection, the DoorProtect Plus model adds an extra layer of intelligence.
The key difference: an integrated accelerometer.This allows the sensor to detect:
Tilt - for example, when a window is slightly opened.
Vibration/impact - attempts to force or damage the protected door or window.
Thanks to these capabilities, DoorProtect Plus can trigger alarms not only when a door is opened but also if an intruder tries to tamper with or break it.
This added functionality does come with a slight trade-off in battery life:
DoorProtect: up to 7 years battery life.
DoorProtect Plus: up to 5 years battery life (due to the accelerometer being active).
Advanced Features
Both versions share several advanced technical characteristics:
Communication range: up to 1,200 meters in open space.
Support for wired NC (normally closed) detectors: the sensors can be paired with external wired contacts if needed, making them even more flexible for complex installations.
Partial arming support: You can arm the system while a window or door remains slightly open (gap between elements), which is particularly useful for ventilation or secure perimeter scenarios.
Summary
Ajax DoorProtect is ideal for basic perimeter protection, detecting open/closed status with a highly reliable magnetic sensor.DoorProtect Plus adds intelligent tilt and impact detection, making it a strong choice for:
High-risk installations (ground floor windows, older wooden doors).
Smart arming scenarios (windows in ventilation mode).
Applications requiring tamper and forced entry protection.
Both sensors integrate seamlessly with the Ajax Hub ecosystem and contribute to robust, flexible perimeter security.
Ajax Curtain
The Ajax MotionProtect Curtain is conceptually similar to a standard MotionProtect sensor - both are based on passive infrared (PIR) detection. However, several important differences define the use cases for each device.
The key component of MotionProtect Curtain is positioned behind a Fresnel lens, inside a slanted cutout at the bottom of the housing. This design is intentional: the sensor must be installed as high as possible - under the ceiling or above a doorway - to achieve the correct downward angle.
Why does this matter?The fundamental difference between Curtain and MotionProtect is the field of view:
Curtain: ultra-narrow beam of just 6°, creating a thin vertical “curtain” of detection.
MotionProtect: wide-angle coverage of 88.5°, suitable for monitoring entire rooms.
As a result:
MotionProtect is intended for general area monitoring.
Curtain is designed specifically for perimeter protection - doorways, windows, corridors, or other narrow passageways.
To further enhance reliability outdoors or in unstable environments, MotionProtect Curtain uses a dual PIR sensor architecture:
The sensor only triggers an alarm if both PIR elements detect identical motion, greatly reducing false alarms.
Key specs:
Detection distance: up to 15 meters.
IP54 ingress protection: suitable for outdoor or semi-outdoor installations.
Communication range: up to 1,800 meters (line of sight to Ajax Hub).
Battery life: up to 3 years on the built-in power cell.
Summary: The MotionProtect Curtain is the optimal choice for creating invisible virtual barriers across vulnerable openings and perimeters, while ensuring high immunity to pets, small animals, and environmental noise.
Ajax Outdoor Section
Part 3, Ajax Detectors Outdoors:
Ajax MotionProtect Outdoor
The MotionProtect Outdoor is Ajax’s dedicated outdoor motion detector - purpose-built to overcome the unique challenges of exterior environments.
Structurally, the device combines two independent PIR sensors stacked vertically inside a single housing. This design addresses the core limitation of outdoor PIR technology: false alarms.
Typical outdoor false triggers include:
Moving tree branches or bushes.
Birds and small animals.
Reflections and sudden temperature shifts caused by sun exposure.
The dual PIR architecture solves this by requiring that both sensors trigger simultaneously:
The upper PIR sensor monitors straight-ahead activity (head/chest level).
The lower PIR sensor monitors lower zones (legs, ground level).
Only when both beams are crossed does the detector send an alarm, filtering out noise such as flying birds or plant movement.
Installation recommendations:
Height: 0.8 to 1.3 meters above ground, aligned with human body height zones.
Detection range: adjustable between 3 to 15 meters via a physical toggle behind the back cover.
Additional protection:
3 anti-masking sensors detect attempts to cover, block, or tamper with the device - a critical feature for outdoor security.
Other key specs:
IP54 protection ensures resistance to dust and water.
Communication range: up to 1,800 meters (line of sight to Ajax Hub).
Battery life: up to 5 years (depending on settings and environment).
Summary: The MotionProtect Outdoor offers robust perimeter protection for gardens, courtyards, driveways, and fenced zones. Its dual PIR and anti-masking features deliver excellent reliability even in complex outdoor conditions, making it one of the most advanced outdoor motion detectors on the market.
Ajax Fire And Leaks Prevention
Part 4, Ajax Fire And Leaks Prevention:
- Ajax LeaksProtect
- Ajax FireProtect
- Ajax FireProtect Plus
Ajax LeaksProtect
The Ajax LeaksProtect is an ultra-simple yet highly effective water leak detector.
Designed for direct placement on flat surfaces in areas prone to potential water leaks, such as under washing machines, dishwashers, bathtubs, heating radiators, or kitchen sinks - it requires no tools or installation assistance.
Operating principle:
Four metallic contacts on the bottom of the device instantly detect the presence of water.
Upon contact with liquid, the sensor transmits a threat signal to the Ajax Hub within 15 milliseconds.
Key specs:
Communication range: up to 1,300 meters (Ajax Jeweller radio protocol, line of sight).
Battery life: up to 5 years with standard operation.
Installation: fully autonomous; no drilling or wiring required.
Ideal for:
Apartments and homes with aging plumbing.
Commercial spaces with critical water-sensitive equipment.
Utility rooms and basements.
Ajax FireProtect and FireProtect Plus
The Ajax FireProtect and FireProtect Plus devices offer comprehensive fire and gas hazard detection in compact standalone units.
Core functions (both versions):
Smoke detection: Optical sensors in sealed smoke chambers monitor air quality and detect the presence of smoke particles.
Temperature monitoring: Rapid response to abnormal temperature increases, ensuring detection of fire risk even in cases without significant smoke.
Additional features:
Built-in 85 dB siren for local alarm signaling - no reliance on external notification devices.
LED-lit logo serves as both an operational indicator and a test button for manual device checks.
Fully autonomous: can operate independently of Ajax Hub, but enhanced features (mobile notifications) are enabled when connected.
FireProtect Plus specific advantage:
Carbon monoxide (CO) detection - a critical life-saving feature.
CO is an invisible, odorless, and tasteless gas produced by incomplete combustion (malfunctioning stoves, heaters, fireplaces).
The Plus version includes an integrated CO sensor capable of alerting occupants to life-threatening gas buildup.
Key specs for both versions:
Communication range: up to 1,300 meters (Ajax Jeweller protocol, line of sight).
Battery life:
FireProtect: up to 4 years.
FireProtect Plus: up to 4 years (slightly reduced due to the additional CO sensor).
Summary of use cases:
FireProtect: Best suited for general smoke and fire monitoring in any room.
FireProtect Plus: Recommended for bedrooms, living areas, basements, and any space with potential CO-producing appliances - provides critical gas leak protection in addition to smoke and heat sensing.
Ajax Controls
Part 5, Ajax Controls:
- Ajax SpaceControl Keyfob
- Ajax Button
- Ajax Keypad
Ajax SpaceControl Keyfob
The Ajax SpaceControl Keyfob is a compact four-button remote control that allows quick system management without using the smartphone app.
Why is it important? In emergency situations, every second counts:
Unlocking a phone, entering a passcode, launching the app, and navigating to system controls can take too long.
SpaceControl lets users instantly trigger commands via tactile physical buttons with haptic feedback and LED status confirmation.
Button functions:
Full circle icon: Arm the system.
Broken circle icon: Disarm the system.
"C"-letter icon: Activate Night mode.
Exclamation point in a circle: Trigger Panic mode - sends an instant alarm to connected monitoring centers.
Ideal for:
Keyholders, staff, elderly family members, and situations where app access may be impractical.
Ajax Button
The Ajax Button is a simple but highly effective panic button.
Use cases:
Personal safety for cashiers, retail staff, and at-risk individuals.
Home emergency signaling.
Discreet alarm triggering in critical situations.
Key specs:
Communication range: up to 1,300 meters (Ajax Jeweller radio protocol, line of sight).
Signal transmission speed: faster than 15 milliseconds.
Battery life: up to 5 years.
Designed for ultimate simplicity - press to trigger an alarm; no secondary actions required.
Ajax Keypad
The Ajax Keypad is a wall-mounted PIN pad designed for fixed access points - ideal for homes, offices, or commercial spaces where multiple users interact with the system.
Core features:
Communication range: up to 1,700 meters.
Battery life: up to 2 years.
Tamper alarm integrated under the rear cover to detect unauthorized removal.
Interface:
Top LED indicators display system status:
Armed
Disarmed
Night mode active
System malfunction (cross in circle)
Standard numeric keypad (0-9) plus clear and asterisk keys.
The asterisk key allows group selection, entry of personal identifiers, or can be configured to trigger predefined system actions (e.g., deactivate fire alarm or activate panic mode).
Dedicated Arm, Disarm, and Night mode buttons at the bottom.
Why use the Ajax Keypad if you already have the app, keyfob, and Ajax Button?
Scalability: In larger homes, offices, or shared spaces, providing individual PINs for each user enables full accountability - you always know who armed or disarmed the system and when.
Duress code: Allows entering a special silent alarm PIN if forced to disarm the system under duress - silently notifies the monitoring center without activating sirens.
Summary
Ajax control devices provide critical redundant control pathways beyond the smartphone app:
SpaceControl offers speed and mobility.
Ajax Button ensures one-press emergency signaling.
Ajax Keypad enables structured multi-user access management and adds a silent duress feature for life-threatening situations.
Together, they strengthen both security and usability of the Ajax alarm ecosystem - and in larger or complex installations, deploying all three devices in tandem is often the best practice.
Ajax Sirens
Part 6, Ajax Controls:
- Ajax StreetSiren
- Ajax HomeSiren
Ajax Sirens: HomeSiren and StreetSiren
Sirens are a critical component of any alarm system. Their purpose is twofold:
Deter intruders immediately by creating a disorienting environment.
Alert occupants and neighbors that a break-in attempt is underway.
Ajax offers two key siren models - optimized for indoor and outdoor use:
Ajax HomeSiren
The Ajax HomeSiren is a compact, unobtrusive indoor siren designed to deliver a powerful audio alert inside protected premises.
Key features:
Acoustic power: adjustable from 81 dB to 105 dB.
Design: fabric-covered front panel conceals the internal buzzer.
Operating range: up to 2,000 meters from Ajax Hub.
Battery life: up to 5 years (replaceable battery).
Status indication: emits sound and LED flashes on system arming/disarming in addition to app notifications.
Tamper protection: built-in tamper alarm triggers if the device is opened.
Ideal for:
Homes, apartments, offices - any indoor space where a loud local alarm is required.
Ajax StreetSiren
The Ajax StreetSiren is a robust, high-power outdoor siren designed to alert the surrounding area and drive intruders away before a break-in progresses.
Key features:
Acoustic power: adjustable from 85 dB to 113 dB - significantly louder than the HomeSiren.
Construction: 5x larger than HomeSiren for enhanced visibility and acoustic performance.
Operating range: up to 1,500 meters from Ajax Hub.
Ingress protection: IP54-rated against dust and water - suitable for year-round outdoor installation.
Tamper protection: Instead of a traditional tamper button, it uses an integrated accelerometer to detect removal or attempts to dislodge the device.
Battery life: up to 5 years.
Status indication: sound and LED flashes signal system arming/disarming and active alarms.
Ideal for:
Building facades, fences, and entrances provides visible and audible deterrence to stop intrusions in progress.
Why Sirens Matter
Sirens are not just a reactive tool - they play an active role in deterring break-ins:
When an intruder triggers a sensor:
The siren emits a deafening noise, immediately escalating stress and panic.
The attacker’s focus shifts from the intrusion to the siren, giving defenders more time to respond.
Neighbors are alerted, increasing the chance of external intervention.
In the case of the Ajax StreetSiren, its IP54 protection and visible design make it an excellent choice for signaling to the outside world that the premises are protected and actively monitored.
Conclusion
Every Ajax installation should include at least one siren:
HomeSiren enhances internal situational awareness.
StreetSiren serves as a powerful visible deterrent to would-be intruders.
Both models integrate seamlessly into the Ajax ecosystem, ensuring instantaneous response, with audio and visual signaling complementing the system’s notifications.