Fibra overview

Fibra is the wired extension of the Ajax ecosystem, designed for commercial, industrial and high-security residential installations where wired reliability is required. Fibra carries both 12V DC power and bidirectional data over a single 2-core cable — no separate power supply is needed at each device.

The protocol operates at 1 Mbit/s and communicates with the hub every 12 seconds by default (configurable down to 6 seconds for critical zones). Tamper detection, signal quality monitoring, and device health reporting are native to the Fibra protocol and visible in the Ajax app in real time.

Hub 2 Plus Fibra specifications

The Ajax Hub 2 Plus is the only hub in the Ajax range that supports Fibra lines. It provides four independent Fibra outputs, each capable of driving a full 2000 m cable run with 100 devices. The hub supplies 12V DC on each line directly from its PSU input.

Signal propagation on Fibra uses differential signalling, making it resistant to electromagnetic interference from 230V wiring, motor drives and fluorescent lighting — a common challenge in commercial and industrial installations.

Fibra cable requirements

Ajax specifies a minimum cable cross-section of 0.33 mm² (22 AWG) for Fibra lines. For longer runs approaching 2000 m, or where the line supplies many powered devices, 0.5 mm² (20 AWG) is recommended to keep voltage drop within tolerance.

Ajax allows a maximum of 2 splices per Fibra line. Additional splices increase resistance and can cause signal integrity issues on longer runs. For shielded cable, ground the shield at the hub end only — double-grounding creates a ground loop.

Fibra line topology

Fibra uses a daisy-chain (series) topology, not a star. Each device connects in line, passing data and power to the next. The final device on the line requires a termination resistor — Ajax ships each Fibra device with a dedicated termination jumper or DIP switch for this purpose.

Hub 2 Plus
  Fibra Line 1 (+) ─────┬─────────────┬─────────────┐
  Fibra Line 1 (−) ─────┤             │             │
                    Device 1     Device 2 … Device N
                    (no term.)   (no term.)  [TERM ON]

Termination resistor:
  Enabled on LAST device only via jumper or DIP switch
  Typical termination: 120 Ω across line differential pair

Signal attenuation:
  ~3 dB per 100 m on 0.5 mm² cable
  Hub app shows "Signal Strength" per device (0–100%)
  Below 20%: relocate device or increase cable cross-section

Power budget check:
  Hub 2 Plus: 400 mA per Fibra line
  DoorProtect Fibra: 0.85 mA standby / 3.5 mA active
  MotionCam Fibra: 0.9 mA standby / 5 mA active (with camera)
  Sum all active currents; leave 20% headroom

Ajax Fibra detector list

All Fibra detectors are managed identically to Jeweller devices in the Ajax app. They appear in the same zone/group structure and support the same automation rules.

Mixing Jeweller and Fibra

Hub 2 Plus supports Jeweller 868 MHz RF devices and Fibra wired devices simultaneously. The combined device limit is 200 — Fibra and Jeweller devices share this pool. A typical commercial installation uses Fibra for main zones (corridors, server rooms, perimeter) and Jeweller for areas where cabling is impractical (roof spaces, listed buildings).

Hub 2 Plus device budget:
  4 × Fibra lines × 100 devices/line = 400 device slots (Fibra)
  Jeweller RF slots:               = up to 200 devices

  COMBINED LIMIT: 200 devices total (Fibra + Jeweller)

  Example commercial installation:
    Fibra Line 1: 60 DoorProtect Fibra (offices, floors 1-3)
    Fibra Line 2: 25 MotionProtect Fibra (corridors + server)
    Fibra Line 3: 10 StreetSiren + Relay Fibra (perimeter)
    Jeweller RF:  15 MotionCam (attic, roof access, listed zone)
    Total: 110 devices (within 200 limit)

Note: each KeyPad Fibra and Relay Fibra also counts
  toward the 200-device limit

Commissioning in Ajax app

Fibra devices are added through the Ajax PRO Desktop or Ajax Security Manager app. After cabling, each Fibra line must be scanned — the hub walks the line and identifies all connected devices automatically without individual QR scanning.

1. Wire all Fibra devices on daisy-chain, enable termination on last
2. Power up Hub 2 Plus (12V DC supply)
3. In Ajax PRO app → Hub 2 Plus → Devices → Add Fibra devices
4. Select Fibra Line (1-4) → Run line scan
   Hub scans line and lists all detected devices
5. Assign each device:
   - Name (e.g. "Server Room Door" or "Corridor PIR Floor 2")
   - Zone / Group
   - Reaction type: Alarm, Tamper-only, or Disabled
6. Check signal strength per device:
   Good: 80-100%, Acceptable: 40-80%, Poor: <40%
7. Test each device: trigger alarm, verify event in hub log
8. Configure arm/disarm delays per zone if required
9. Link to monitoring station CMS (Ajax Cloud → Monitoring API)

Fibra vs traditional wired security