Aiwa MF 355RF - Manual (Page 74)

Manufacturing Reset (981):
Press and hold the setup key until the red LED blink twice than release.
Press now the following keys 9 8 1.
Please note the following blinkings for the red LED:
For the MF 150 and MF 250 the red LED will blink twice followed by a short
delay and one long blink.
For the MF 350 and MF 355 RF the red LED will blink twice followed by a
short delay and another two blinks.