Sony SDM-S51R Mode D'emploi page 15

x Locking the menus and controls
First press the M/m buttons to select (MENU LOCK)
and press the OK button. Then press the M/m buttons
and select ON.
Only the 1 (power) switch, and (MENU LOCK) of the
option menu will operate. If any other items are selected, the
mark appears on the screen.
To cancel the menu lock
Repeat the procedure above and set and (MENU LOCK) to OFF.
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