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Guide to the discontinued JSB Firedex BiWire fire alarm system

The Firedex was a biwire fire alarm system launched by JSB in the late 1990’s and is now part of the Eaton group. This system allowed detectors, manual call points and sounders to be fitted onto the same wire, meaning only a single cable would be required for each zone.

Unfortunately due to changes in the third party certifications required for fire detection equipment, the Firedex biwire system was discontinued in July 2013. Despite not meeting these requirements, any existing systems which are running normally are still compliant providing they are serviced & maintained in accordance with BS5839.

Where things become a little more complicated are scenarios in which existing systems need changing. From our experience of supporting these systems we have devised the following scenarios and have outlined your options for each.

My panel is faulty or I require a larger size

Unfortunately this is the worst case scenario as there is no panel available which can support the vast majority of original Firedex biwire devices.

The whole system would need to be changed for the current Eaton Biwire Ultra system and the only existing devices which can be carried forward are the common mounting bases (model FXN520).

I need to add/replace existing device(s)

Expanding or replacing devices on an existing system, providing the panel is functional, is feasible. The following devices from the current Eaton range are compatible with the obsolete Firedex panels.


Firedex supports the FXN922 detector so this can be used to either replace existing detectors* or to expand a system with new detectors.

The FXN922 is a 5-in-1 detector which combines both optical smoke and heat technologies in one unit. The mode of detection can be set via an onboard dip switch. Depending upon requirements the FXN922 can be used with the FXN520 common mounting base or the EF5021BWS sounder base.

*When replacing an existing detector which is fitted onto a sounder base, then this sounder base must be a FXN521BWS or EF5021BWS model. If this is not the case then the sounder base must also be changed to the current EF5021BWS.

Manual call points

The current FX201 manual call point is supported which can be used to extend a system or replace an existing MCP.


All of the Eaton BiWire Ultra sounders are supported.