How to Integrate AJAX with Control4, Homey & Loxone (Modbus)

Connect your AJAX alarm to your building automation so an armed state can start an away routine, an alarm can trigger a programmed response, and your control interface can send arm, disarm or night-mode commands. The AJAX-MBTCP Gateway by Elausys provides the hardware link through Modbus TCP for Loxone, Control4, Homey, Node-RED and other compatible platforms.

AJAX-MBTCP at a glance

Hardware gateway: Check the product page for current pricing, availability and delivery details.
Alarm integration: up to 4 areas, 96 detector event coils, area status and power-fault feedback.
Local status monitoring; cloud-based control: alarm events arrive over the local network. Arm, disarm and night-mode commands require internet access and the AJAX cloud connection.
No additional gateway subscription. Your automation platform may require its own driver or app.
30-day money-back guarantee and 2-year warranty: see the shop for applicable terms.

View AJAX-MBTCP pricing and order

Unsure whether it fits your installation? Ask Elausys about compatibility with your AJAX hub model, automation platform and intended use.

Is this gateway right for your project?

A good fit: showing armed/disarmed states in your automation interface, starting away or night routines from alarm-state changes, responding to alarm events, or sending area-control commands.

For everyday motion-controlled lighting: AJAX detectors do not provide unrestricted activity reporting while the system is disarmed. Always Active devices can report events, but they also trigger alarms while disarmed. This setting is not a workaround for ordinary occupancy sensing.

Before ordering, check that you have:

An AJAX hub with Ethernet and support for local SIA event transmission.
An automation platform or driver that supports Modbus TCP Read Coils (0x01) and, if control is required, Write Single Coil (0x05).
A 12–30VDC power supply, Ethernet connection and space for a 2 SU DIN-rail module.
Access to configure the AJAX hub and your automation platform.
Internet access and the security-company invitation described below if you need arm/disarm control.

For an installation with professional monitoring, confirm the reporting arrangement with your monitoring provider before changing its configuration. See the monitoring FAQ below.

What Is a Modbus TCP Alarm Gateway

A Modbus TCP alarm gateway is a hardware interface that connects a professional alarm system to the Modbus TCP protocol, exposing alarm statuses as readable registers and accepting control commands from any Modbus TCP master on the network.

In practical terms, this means your automation platform — whether it's a Loxone Miniserver, a Control4 controller, a Homey hub, a Node-RED instance, a PLC, or a BMS — can read alarm events in real time and send arming and disarming commands back to the alarm system.

Why does this matter for integrators?

Without a gateway, AJAX alarm systems and building automation platforms operate as separate islands. The alarm detects an intrusion, but the building doesn't respond. The client arms the system at night, but lighting and blinds don't adjust.

A Modbus TCP alarm gateway eliminates this disconnect. It maps AJAX alarm states to standard Modbus coils that any automation platform can read and act on.

Key terms to understand:

Modbus TCP — an industry-standard communication protocol used by building management systems, PLCs, SCADA platforms, and home automation controllers to exchange data over Ethernet
Coils — single-bit Modbus registers used by the gateway to represent alarm statuses (read-only) and control commands (read/write)
Bidirectional communication — the gateway both exposes alarm statuses as readable coils and accepts arming/disarming commands via writable coils
Zone status — the state of individual alarm sensors (motion detectors, door/window contacts, etc.) mapped to dedicated Modbus coils
Area control — the ability to arm, partially arm (night mode), or disarm alarm partitions by writing to command coils
SIA protocol — the standard alarm communication protocol used by AJAX to transmit events to the gateway over the local network

AJAX Meets Modbus TCP

Why AJAX — and why Modbus TCP?

AJAX Systems has become one of the most popular professional alarm platforms in Europe. Known for its wireless reliability, sleek design, and user-friendly app, AJAX is increasingly specified in residential and commercial projects alongside automation platforms of all kinds.

After the success of the AJAX-KNX Gateway, integrators working with Loxone, Control4, Homey, Node-RED, and PLC-based systems asked for the same integration capability. Modbus TCP was the natural answer — it's the common language that connects virtually every automation platform on the market.

What the AJAX-MBTCP Gateway delivers

The Elausys AJAX-MBTCP Gateway exposes the following alarm functions to compatible Modbus TCP clients:

Up to 4 area controls — arm and disarm AJAX partitions by writing to command coils from any Modbus TCP master
Global commands — arm all areas, disarm all areas, or activate/deactivate night mode (partial arm) with dedicated global coils
6 area status feedbacks per area as read-only coils — disarmed, armed, partial armed (night mode), fire alarm, panic alarm, intrusion alarm
Up to 96 detector statuses mapped to individual Modbus coils — read detector events from your automation platform when the system is armed, in night mode, or when devices are set to Always Active, subject to AJAX zone-reporting behaviour
Power supply monitoring — AC failure and battery failure status available as Modbus coils
Standard Modbus TCP protocol on port 502, supporting up to 2 simultaneous client connections

What does each automation platform need?

The gateway is a Modbus TCP server. Your automation platform acts as the client and must map the gateway's coils to its own controls and automation logic.

Loxone: use the Miniserver's Modbus TCP connection over Ethernet, configured in Loxone Config. The Modbus RTU Extension is not needed for this TCP connection.
Control4: use a Modbus TCP driver that supports the required coil reads and writes. Confirm the driver, licensing and setup with your Control4 integrator before ordering.
Homey: use a compatible Modbus TCP app and supported Homey model. Confirm support for the required coil functions; app availability alone does not establish compatibility with every Homey setup.
Node-RED: use Modbus TCP nodes to read status coils and write command coils, then build the required flows.
PLCs, BMS and SCADA: configure a Modbus TCP client with the gateway's coil map and the functions needed for your project.

The gateway supplies the interface to AJAX; the platform's driver, app and automation logic still need to be configured. Check your platform requirements with Elausys before choosing components.

Practical Implementation: How to Set Up the AJAX-MBTCP Gateway

Step-by-step integration process

Step 1 — Hardware installation

Mount the AJAX-MBTCP Gateway on a DIN rail (2 SU). Connect the external 12–30VDC power supply and the RJ45 Ethernet cable on the bottom side of the module. The gateway communicates with the AJAX Hub over the local network to receive events. For arming and disarming commands, internet access is required — the connection is established through the AJAX secured cloud using a fully encrypted protocol, identical to the one used by the AJAX mobile application.

Step 2 — Configure the AJAX Hub for SIA Events

On the AJAX side, configure your AJAX Hub to send SIA Events to the gateway's IP address on port 2410. Open the Space Settings, then Security Companies, then Monitoring Station and enter the gateway's IP address, port 2410, and a 3-letter object number of your choice.

Step 3 — Invite Elausys as Security Company (for area control)

If you need bidirectional control — meaning you want to arm or disarm AJAX areas from your automation platform — you must invite Elausys as a Security Company using the email address provided in the manual in the AJAX app. This grants the gateway the necessary permissions to send commands back to the AJAX Hub.

This invitation is required for gateway control commands; local SIA monitoring does not require it.

Step 4 — Configure the gateway via web interface

By default, the gateway's IP address is 192.168.1.51. Connect a laptop to the gateway and open a web browser to access the configuration page.

Set a fixed IP address appropriate for your network
Enter the AJAX Hub ID (8 characters, found at the bottom of Hub status in the AJAX app)
Set the Partition Mode to match your AJAX Group mode from the Space Settings (Partition OFF for global hub mode, Partition ON for group mode)
Set the number of areas to match the group configuration in the AJAX system

The Modbus TCP interface is enabled by default on port 502 with Unit ID 1 and requires no additional configuration.

Step 5 — Configure your Modbus TCP master

On your automation platform (Loxone, Control4, Homey, Node-RED, PLC, etc.), add a new Modbus TCP connection pointing to the gateway's IP address on port 502 with Unit ID 1. Map the relevant coils to your automation logic:

Command coils (0x0000–0x000A): write to these to arm, disarm, or activate night mode
Area status coils (0x000B–0x002E): read these to get real-time area status (armed, disarmed, fire, intrusion, panic, partial armed)
Detector status coils (0x002F–0x008E): read these to get individual zone/detector states
System status coils (0x008F–0x0090): read these for AC and battery fault monitoring

Ensure your Modbus master's polling interval is shorter than 60 seconds to avoid the gateway's automatic connection timeout.

Automation scenarios

Intrusion response: An intrusion is detected on Area 1 → the gateway updates the intrusion alarm coil → your Loxone Miniserver, Control4 controller, or PLC reads the status change and triggers your programmed response: escape route lighting activates, exterior lights illuminate the perimeter, and blinds open. The building doesn't just sound a siren — it responds through your automation platform.
Fire alarm coordination: A fire alarm triggers on Area 2 → the fire alarm coil goes active → your automation system reads the change and executes the emergency sequence: all blinds open to clear escape routes, emergency lighting activates, ventilation shuts down. One alarm event, full building response — orchestrated by your Node-RED flow, PLC logic, or BMS programming.
Night mode activation: The client arms the system from the AJAX app → the gateway updates the armed status coil → your Homey, Loxone, or Control4 reads the new state and triggers the night routine: all lights off, blinds close, heating shifts to setback mode, presence simulation activates. Or the reverse — your automation platform sends an arm command via the global command coil, and the entire building shifts to security mode from a single button press on a wall panel.

Does this match your project? View the AJAX-MBTCP Gateway, or ask Elausys to check your setup before ordering.

Common mistakes to avoid

Not understanding zone reporting behaviour — AJAX sensors only report zone status when the system is armed or in night mode. Setting devices to Always Active enables daytime reporting, but also means those zones will trigger the alarm when the system is disarmed. Plan which zones genuinely need 24/7 reporting.
Not inviting Elausys as Security Company — area control (arm/disarm commands) will not work without this step. Internet access is also required for arming/disarming commands.
Incorrect area count with AJAX groups — when groups are enabled in AJAX, at least two areas must be configured on the gateway to switch from global to individual group commands. Configuring only one area when groups are active will result in incorrect behaviour.
Expecting disarm to exit Night Mode — when groups are enabled, disarming a group does not disable Night Mode. You must explicitly send a Partial Arm OFF command. Design your automation logic to handle this independently.
Modbus TCP connection timeout — the gateway automatically closes idle connections after 60 seconds. Ensure your Modbus master polls at intervals shorter than 60 seconds to maintain the connection.
Writing to read-only coils — attempting to write to status coils (addresses 0x000B and above) will return a Modbus exception. Only command coils (0x0000–0x000A) accept write operations.

Choose your next step

The AJAX-MBTCP Gateway brings AJAX alarm events and area control into your Modbus TCP automation project. Status coils are read-only; separate command coils provide arm, disarm and night-mode control through the AJAX cloud connection.

Ready to order?

View the AJAX-MBTCP Gateway — pricing, availability and ordering

Need to confirm compatibility first?

Ask Elausys about your installation. Include your AJAX hub model, automation platform and version, desired functions, and whether a monitoring company already receives alarm events. For Control4 or Homey, include the proposed Modbus driver or app if known.

Planning the configuration?

Read the AJAX-MBTCP documentation and coil map to check connections, settings and command addresses.

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Frequently Asked Questions

What AJAX systems are compatible with the AJAX-MBTCP Gateway?

Use an AJAX hub with Ethernet and support for SIA event transmission over the local network. Check your exact hub model and available monitoring-station settings before ordering; Elausys can help confirm compatibility.

Can I arm and disarm the AJAX system from my Loxone, Control4, or Homey?

Yes, with a compatible Modbus TCP client or driver that supports Write Single Coil (0x05). Enable the gateway's control connection, invite Elausys as a Security Company as described in the manual, and provide internet access for commands through the AJAX cloud. Your automation platform must then map the command coils to its controls.

How does the Modbus TCP communication work?

The gateway operates as a Modbus TCP server (slave) on port 502 with Unit ID 1. It supports Read Coils (function code 0x01) for reading status and Write Single Coil (function code 0x05) for sending commands. All data is mapped to single-bit coils — 145 coils in total covering area commands, global commands, area statuses, detector statuses, and system status.

Can I use AJAX motion detectors for automation (e.g., lighting control)?

Detector events can trigger automation when the AJAX system is armed or in night mode. They do not provide unrestricted motion reporting while disarmed.

Devices set to Always Active (24hrs) can report while disarmed, but they also trigger the alarm in that state. Use this only when continuous alarm protection is intended. For ordinary daytime occupancy or corridor-lighting control, plan for dedicated automation sensors.

How many zones and areas does the gateway support?

The gateway supports up to 96 detector statuses mapped to individual Modbus coils and up to 4 areas with full control (arm/disarm) and 6 status feedback coils per area. Global command coils allow arming, disarming, and night mode control across all areas simultaneously.

Can I use the gateway with Node-RED?

Absolutely. Node-RED's Modbus TCP nodes can connect directly to the gateway on port 502. You can read detector status coils, monitor area statuses, and write to command coils — all within standard Node-RED flows. This gives you unlimited flexibility to build custom automation logic around AJAX alarm events.

What happens if the internet connection fails?

Local SIA monitoring continues while the AJAX hub, gateway and local network remain connected and powered. Arm, disarm and night-mode commands from the gateway require the AJAX cloud connection and are unavailable without internet access.

Does the gateway require cloud connectivity?

The gateway communicates with the AJAX Hub over the local network via Ethernet to receive alarm events — no cloud dependency for monitoring. If arming or disarming commands are used, the connection is established through the AJAX secured cloud using a fully encrypted protocol, identical to the one used by the AJAX mobile application.

Can I connect multiple Modbus TCP masters simultaneously?

Yes. The gateway supports up to 2 simultaneous Modbus TCP client connections. This allows, for example, a Loxone Miniserver and a BMS to both read alarm statuses at the same time. Idle connections are automatically closed after 60 seconds of inactivity.

What happens if the Ethernet connection between the gateway and the AJAX Hub drops?

The front panel Connected LED will turn off, indicating communication loss. Detector status coils will hold their last known state until communication is restored.

Can I keep my existing monitoring service?

This depends on how your monitoring service receives events. In the setup described here, the AJAX hub's SIA reporting destination is the AJAX-MBTCP Gateway, so the same direct SIA feed cannot also be used by an external monitoring station.

A monitoring provider may instead receive events through Cloud Signaling. Confirm that arrangement with your provider before redirecting SIA reporting. Contact Elausys with your existing monitoring setup if you need help checking the gateway configuration.

How is the gateway physically installed?

The AJAX-MBTCP Gateway is DIN rail mounted (2 SU), requires an external 12–30VDC power supply, and connects to the local network via a standard RJ45 Ethernet cable.