Module for connecting Ajax security systems to third-party VHF transmitters

Instant alarm transmission without Internet

vhfBridge is a transponder that provides a hub with an additional channel to communicate with a monitoring station. With vhfBridge you can use Ajax systems in cities where Internet connection is unstable, in nature reserves, mountain and desert areas.

Alarms and events of the system are transmitted via VHF radio waves over tens of kilometres1. vhfBridge can be used as a primary or a backup communication channel.
Instant alarm transmission without Internet

Reliability and versatility by design

Reliability and versatility by design
You can buy vhfBridge without a casing
You can connect any VHF transmitter with relay inputs to vhfBridge

Elaborate autonomy

You can build in a 7 Ah backup battery inside a vhfBridge casing. It will feed a VHF transmitter with up to 2A current consumption. Therefore, the transmitter doesn't need to have a separate battery, which makes maintenance less frequent.

In case of a power outage at a facility, the transponder and the transmitter operate on a backup battery for up to 75 hours4 while still transmitting events to a central monitoring station.
  • Up to 75 hours4 of autonomous operation
  • Place for a 7 Ah backup battery
Elaborate autonomy

Adjustable signalling

Get only events you need. You can configure each vhfBridge output in the Ajax app: set an event or disable it.
Adjustable signalling

Uncompromised security of communication

vhfBridge communicates with a hub via an encrypted Jeweller radio protocol. It guarantees continuous interaction of all security system devices. The radio protocol uses frames to synchronize device communication sessions, authentication to prevent forgery, and encryption to protect against data theft.
Connection with a hub at a distance of up
to 1,800 meters
Alarm transmission within
0.15 seconds
Hub ping interval
from 12 seconds

Hassle-free installation

Similar to other Ajax devices, vhfBridge connects to a hub in the app by scanning a QR-code. The transponder casing has perforated areas for more organized wiring. Outputs are configurable with Ajax apps for smartphones and computers.
  • Adding to the system by scanning a QR-code
  • Mounting on a wall
  • Connecting of a VHF transmitter
  • Setting up with an app
Hassle-free installation

Tech specs

White and black
Transponder for communication with the monitoring station via a VHF transmitter
Number of potential outputs
Output types
Positive trip and negative trip (depends on the settings)
Transmission types
Pulse and bistable (depends on the settings)
Recommended VHF transmitters
Hawk VHF Alarm Transmitter from FSK Electronics
TX750C from RDC
TR-41 from Puper
Compatible with Ajax central units
Operates with Hub 2, Hub Plus, Hub 2 Plus
Compatible with Ajax range extenders
Compatibility with third-party VHF radio transmitters
vhfBridge connects to any VHF transmitter with relay inputs

Recommended models
Support for photo verification of alarms
Primary power supply
100–240 V, 50/60 Hz
Backup power supply
12 V DC, up to 75 hours of power for a transponder and a transmitter
Supported battery type
12 V battery with a full charge cycle of up to 30 hours.

The maximum battery size installed in the casing should be 150 × 64 × 94 mm
Recommended battery type
12 V battery with a capacity of 4 Ah or 7 Ah

Backup battery is not included in the set
VHF transmitter power
12 V DC, 2 A
Protecting against forgery
Jamming notifications
Tampers against opening and removal
Backup battery
Jeweller radio protocol
Communication range — up to 1,800 meters in a line of sight
Two-sided communication between devices
Operating frequencies: 868.0–868.6 MHz
Auto-regulated radio signal power: ≤ 25 mW
Blocking encryption based on the AES algorithm
Detector ping interval: 12–300 seconds
Frequency hopping

Learn more about Jeweller
Maximum radio signal power
≤ 25 mW
Protection class
Operating temperature range
From –10°C to +40°C
Operating humidity
Up to 75%
Overall dimensions
196 × 238 × 100 mm (with casing)
145 × 89 × 51 mm (without casing)
840 g (with casing)
165 g (without casing)
Warranty service for 24 months from the date of sale.

Learn more
Complete set
Power cable
12 V battery connection cable
Installation kit
Casing (depends on a set)
Quick start guide
10 years
1 The distance depends on the transmitter, the terrain, and the weather. The maximum range varies in each particular case.
2 A backup battery is not included in the set.
3 vhfBridge can be sold without a casing.
4 When using a 7 Ah battery.

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