Canon MultiPASS C560 User Manual page 330

Images on received faxes from the MultiPASS are spotted or dirty.
The receiving fax machine may not be working properly.
I
Check the MultiPASS by making a copy (see
the receiving fax machine.
Cannot send or receive using Error Correction Mode (ECM).
The other party's fax machine may not support ECM.
I
Some fax machines do not support ECM. If the other party's fax machine does not support
ECM, then the document is sent or received in normal mode without error checking.
ECM may be disabled.
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Make sure ECM is on. (If you are using the Desktop Manager, see the MultiPASS Desktop
Manager Software Guide. If you are using the operation panel, see the Stand-alone Fax
Manual.)
Chapter 8
page 4-21). If the copy is clear, the problem may be in
Troubleshooting 8-35