Brother MFC640CW Service Manual page 125

(14) A head/carriage unit is assigned a property code that represents the properties unique to that
head/carriage unit. The property code is printed on a property label that is attached to the
carriage-head flat cable and the machine.
When you remove the head/carriage unit and store it separately from the machine, remove the
property label from the machine and store it together with the head/carriage unit.
If you replace the head/carriage unit, attach the property label that comes with the new
head/carriage unit to the machine as shown below.
Viewed from the bottom
Bosses
Head/carriage unit
5 - 3 9
Property label for
head/carriage unit
Property code
(13-digit)
Confidential