The data being sent from the operator panel is corrupted and the passenger panel is reporting the error as “Bad Char” or bad character received.

There are no settings that could be wrong that will produce this error, and you will need to confirm if the fault is with the cables, passenger panel or operator panel.

If this is a new installation and the passenger panels produce the fault straight away when first connected, check the passenger display cable and swap for a known good one.

Try a good passenger panel in place of one of the units showing the error message.  If the fault remains, try changing the cables.  If this doesn’t fix the problem then we will have to assume the operator panel communications port is at fault, and will need to be repaired or replaced.