How do I fault-find a panel with no microphone audio?

Owned by Graham Balchin
May 31, 2018
3 min read

If a panel connected to the matrix has functioning keys and displays but when a key is pressed to speak and a solid red tally is shown but no audio is heard at the destination try the following tests to fault find the possible cause of no audio.


If it is connected to a Gemini matrix try tests 1 to 3. For Messenger, skip test 2.

Step-by-step guide


  1. If the panel cut switch is assigned to cut the panel mic, check the panel cut switch is not pressed and the cut indicator is not illuminated.
  2. On the Gemini front panel, select Tools > Monitor. On this screen make sure the ‘Inputs’ option is showing in the bottom right corner. Now select the port number the panel is connected to and then choose ‘Levels’.

The level meter is now displaying the audio from the panel microphone coming into the matrix. If you scratch or speak into the microphone it should show around 0 dB level on the meter. If not move to test 3.

3. Swap this panel with a known working panel, use the same cable between the panel and matrix. Does the fault follow the panel or is the known working panel now showing the same defect when plugged to the same matrix port? If the replacement panel works correctly this suggests a panel fault - go to test 5. If the replacement panel still does not work this suggests a cable fault - go to test 4 to confirm.

4. Swap the cables on the AEB port connections on the rear of the matrix. Take another cable from a matrix AEB port with a known working cable and known working panel connected and plug this into the AEB port with the no audio fault. If the audio fault is still present this would indicate a fault with the matrix port, swap the 700-26-27 AEB module to confirm.

5. Take an RJ45 patch lead and cut off one connector around 15 cm from the end. Then strip back the wires and make two soldered connections.

  • Join the Blue wire to the Brown wire.
  • Join the Blue/White wire to the Brown/White wire.

With this you now have a short RJ45 cable with two loopback connections. If you plug this cable into the ‘Matrix’ connector on the panel this will now route the audio from the panel’s mic to the panel’s speaker. If no audio is heard, then this would indicate a defect with the panel, if audio is present, the fault is either matrix related or the cable between the panel and the matrix.


If the defect appears to be with the panel, remove the mains power to the panel, remove the set screws holding the rear cover and once the rear cover is removed check to see the microphone cable is fully seated to the connector on the main board.




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