Brother FAX-921 - Manual (Page 160)

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(6) ID checking
Code 1 Code 2 Causes
63 01 Password plus "lower 4 digits of telephone number" not coincident.
63 02 Password not coincident.
63 03 Polling ID not coincident.
63 04 Entered confidential mail box ID uncoincident with the mail box ID.
63 05 Relay broadcasting ID not coincident.
63 06 Entered retrieval ID uncoincident with that of the mail box ID.
(7) DCN reception
Code 1 Code 2 Causes
74 DCN received.
(8) TCF transmission/reception
Code 1 Code 2 Causes
80 01 Fallback impossible.