Factory Reset (Initialize Memory)

1. Turn off the Proteus FX.
2. Hold down the [MASTER] and [EDIT] buttons.
3. While holding the buttons, turn the power on.
4. Continue holding until the display reads 'INITIALIZING MEMORY'.
5. Release the buttons. The unit will reset to factory defaults.

Source: Proteus FX — proteusfxownersmanual (manual)