Brother MFC640CW Service Manual page 237

(4) Press the Menu/Set key (OK key on MFC820CW, Set key on DCP340CW).
The machine beeps, shows the "INPUT ACCEPTED" on the LCD, and writes the entered
property code into the EEPROM. Then it returns to the initial stage of the maintenance mode.
NOTE: If the entered data contains any checksum error, the machine beeps, shows the
"INPUT ERROR," and then returns to the ready-to-enter state. Go back to step (3).
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