Jeweller Protocol Characteristics

Ajax Systems (Kyiv, Ukraine) developed the Jeweller protocol for the Ajax smart security ecosystem. Jeweller operates at 868.0-868.6 MHz (EU frequency band), using TDMA (time-division multiple access) with each device assigned a fixed transmission slot — collision-free communication at full mesh load.

Key specifications: 2000m open-air range (Ajax Hub 2 Plus to detector), 7.3-second polling interval (hub polls each device, detects missing response within 2 polling cycles), AES-128 encryption with per-device keys, Wings channel (separate 2.4 GHz) for configuration and OTA updates without interfering with the 868 MHz security channel. Maximum 100 devices per Hub 2 Plus, 25 Ajax hubs per site (multi-hub installations).

Ajax Hub 2 Plus Setup

Hub 2 Plus: dual SIM (2G/LTE) + Ethernet. Configure in Ajax mobile app (iOS/Android). Add devices by scanning QR code or entering serial number. Device placement: Ajax app shows signal quality in real-time during installation — minimum 2 signal bars required. Below 2 bars: add ReX range extender (868 MHz bidirectional repeater, mains-powered, up to 2 hops).

Jeweller sensor portfolio relevant to KNX projects: MotionCam (PIR + camera, 12m, photo on trigger), DoorProtect Plus (magnetic contact + shock + tilt sensor), GlassProtect (glass break, 9m), LeaksProtect (flood/water, 3 sensing points), FireProtect Plus (optical smoke + CO + heat), ThermoSensor (temperature range monitoring), WaterStop (motorised water valve control).

KNX Integration via Ajax API

Ajax Hub 2 Plus exposes a REST API (Ajax API v1, documented at ajax.systems/developers). Authentication: API token per hub account. Webhook support: configure webhook URL in Ajax app (Hub settings > API > Webhooks). Hub sends HTTP POST to your webhook endpoint on each event: sensor triggered, arm/disarm, tamper, battery low.

Webhook payload (simplified):
  eventType: "MOTION"
  deviceId:  "sensor-id-abc"
  hubId:     "hub-xyz"
  timestamp: 1707000000

Node-RED flow:
  [http in] POST /ajax-webhook
    → [function] map eventType to KNX GA
        MOTION       → GA 2/3/1 = 1 (DPT 1.001)
        OPEN         → GA 2/3/5 = 1 (DPT 1.001)
        ALARM        → GA 8/0/20 = 1 (DPT 1.001)
        TAMPER       → GA 8/0/21 = 1 (DPT 1.001)
        LOW_BATTERY  → GA 8/0/22 = 1 (DPT 1.001)
    → [knx out] send telegram to KNXnet/IP tunnel

Arm/Disarm from KNX

Ajax API arm command: POST to the ajax.systems API arm endpoint with JSON body specifying the group ID and arm mode. Trigger from KNX: when KNX GA 8/2/0 (arm request, DPT 1.001) receives value 1, Node-RED sends the HTTP POST to the Ajax API arm endpoint. When KNX HVAC presence GA goes to 0 (all rooms unoccupied), automatically arm Ajax security.

KNX GA 8/2/0 (arm request) = 1
  → Node-RED HTTP POST to ajax.systems API
  → Body: {"groupId": "all", "state": "ARMED"}
  → Response: 200 OK (armed successfully)
  → KNX GA 8/2/10 (arm confirmed) = 1

KNX GA 5/5/99 (occupancy master) = 0 (unoccupied)
  → Wait 120 seconds (avoid false trigger on brief absence)
  → IF still 0: POST arm command
  → Ajax sends push notification: "System armed"

KNX GA 8/2/0 = 0 (disarm request)
  → POST disarm command to Ajax API
  → KNX GA 8/2/10 = 0 (disarmed confirmed)

Note: disarm requires valid user code in API body
  Store code in Node-RED environment variable
  never hardcode in flow JSON visible in exports

MotionCam Photo Verification

The Ajax MotionCam unique feature: on motion detection during armed mode, the camera takes a series of photos (3-second burst at 2fps) and transmits them via Jeweller to the hub, then to the monitoring centre or app. This allows visual verification of the alarm cause before dispatching security response.

From a KNX perspective: when MotionCam triggers, the Ajax API sends a webhook with eventType ALARM and an associated photoUrl field (temporary URL, valid for 24 hours). The Node-RED bridge can save this URL to a KNX string object (DPT 16.001) or trigger a notification to the building management screen.