Brother MFC-9420CN Service Manual page 273

(5) Command reception [checking the NSF and DIS after transmission of NSS and DCS]
Code 1 Code 2
50 01
(6) ID checking
Code 1 Code 2
63 01
63 02
63 03
(7) DCN reception
Code 1 Code 2
74
(8) TCF transmission/reception
Code 1 Code 2
80 01
(9) Signal isolation
Code 1 Code 2
90 01
90 02
Vertical resolution capability changed after compensation of
background color.
Password plus "lower 4 digits of telephone number" not
coincident.
Password not coincident.
Polling ID not coincident.
DCN received.
Fallback impossible.
Unable to detect video signals and commands within 6 seconds
after CFR is transmitted.
Received PPS containing invalid page count or block count.
9 - 1 7
Causes
Causes
Causes
Causes
Causes
Confidential