Dear Valued Partner,

Mircom has prepared this bulletin to notify our valued partners that we have recently received reports regarding a field issue concerning certain addressable loop devices experiencing communication challenges with some of our FX-400/FX-401 series panels. In response, our team has promptly developed a firmware solution to address this issue.

While implementing a firmware upgrade in the field is a straightforward and swift process (please refer to TIB-FAP-24-050  for detailed instructions), we have implemented proactive measures to rectify the recent field issue and update our current stock of FX-400/FX-401 series panels with the latest firmware upgrade. This will reduce the likelihood of the current field issues and communication challenges occurring in any future FX-400/FX-401 series panels dispatched to our customers. It is important to note that this firmware upgrade will not alter the existing job configuration within the FX-400/FX-401 series panels.

Please note that the present field issue has only been identified under specific circumstances and configurations. Therefore, we kindly ask that you review the conditions set out below to ascertain whether any further action is required on your part to resolve the outstanding field issue:


  1. Your configuration uses a single SLC loop without a dual loop expander (ALC-480);
  2. In the single SLC loop, there are under 20 devices present, with at least one input module, MIX-4040, or one MIX-4041 installed with Class B End of Line (EOL) wiring; and
  3. The label on the FX-400/401 panel shows “SO-435 V1.0.29”.

If all three of the above-noted conditions (1, 2 & 3) are met, please contact our technical support team for guidance at: [email protected]. Alternatively, you may directly download the FW V2.1.9 upgrade (or a more recent firmware upgrade, with a number greater than 2.1.9), through our ESD website for the latest in-field firmware upgrade. We recommend saving a record of the latest job configuration for future reference.

It is important to note that installed units not meeting the above-noted conditions remain unaffected and will continue to function without any issues or interference.
We thank you for your continued support and cooperation. If you have any questions or comments, please contact us directly at: [email protected]

Thank you,

Mircom Group of Companies