Sony SDM-S51R Operating Instructions Manual page 15

• Locking the menus and controls
First press the t_/_ buttons to select O-n (M ENU LOCK)
and press the OK button. Then press the t_/_ buttons
and select ON.
Only the _3 (power) switch, and O-n (MENU LOCK) of the
option menu will operate, if any other items are selected, the O'_
mark appears on the screen.
To cancel the menu lock
Repeat the procedure above m_dset and O'11 (MENU LOCK) to OFF.
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