Brother MFC 1780 - Manual (Page 13)

3
I N T R O D U C T I O N
ECM (Error Correction Mode)
The Error Correction Mode (ECM) is a way for the fax machine to check the
integrity of a fax transmission while it is in progress. ECM transmissions are
possible only between machines that both have the ECM feature. If they do, you
may send and receive fax messages that are continuously checked for their
integrity.
Sufficient memory must be available in your fax machine for this feature to work.