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At my company we have 3 7775s, 1 of which is supposed to be our main fax machine as well as Copy, Scan and Print. But, if I install the fax board and hook up to the fax line, eventually (could be ~1hr up to a week) it will cause the machine to have a fatal error (screen has a red background) and I have to uninstall the fax board. Restarting the machine brings it back to the error screen.
Now, I highly doubt it is anything to do with the machine or fax board because one of our other 7775s used to sit where the problem machine is and the problem stayed with the jack, it did not follow the machine. We have changed extensions from the 66 block, put on a line filter, ran the line through the printers power block on the fax in/out ports and even had our carrier come out and replace the channel back that the line runs off of (dedicated analog). The printer does not experience this issue without the fax board and the line does not cause issues on an old Canon fax machine that we are forced to use. This problem is driving me insane. Thanks in advance for the help.