Brother FAX-T94 - Manual (Page 23)

INTRODUCTION 1 - 9
ECM (Error Correction Mode)
The Error Correction Mode (ECM) is a way for the fax machine to
check a fax transmission while it is in progress. ECM transmissions
are only possible between machines that both have this feature. If
they do, you may send and receive fax messages that are
continuously being checked by the machine.
The fax machine must have enough memory for this feature to work.